Add m-esr52 at 52.6.0

7 files changed, 2546 insertions, 0 deletions

diff --git a/widget/android/jni/Accessors.h b/widget/android/jni/Accessors.h
new file mode 100644
index 0000000000..fe2cbc9d4c
--- /dev/null
+++ b/widget/android/jni/Accessors.h
@@ -0,0 +1,274 @@
+#ifndef mozilla_jni_Accessors_h__
+#define mozilla_jni_Accessors_h__
+
+#include <jni.h>
+
+#include "mozilla/jni/Refs.h"
+#include "mozilla/jni/Types.h"
+#include "mozilla/jni/Utils.h"
+#include "AndroidBridge.h"
+
+namespace mozilla {
+namespace jni {
+
+namespace detail {
+
+// Helper class to convert an arbitrary type to a jvalue, e.g. Value(123).val.
+struct Value
+{
+    Value(jboolean z) { val.z = z; }
+    Value(jbyte b)    { val.b = b; }
+    Value(jchar c)    { val.c = c; }
+    Value(jshort s)   { val.s = s; }
+    Value(jint i)     { val.i = i; }
+    Value(jlong j)    { val.j = j; }
+    Value(jfloat f)   { val.f = f; }
+    Value(jdouble d)  { val.d = d; }
+    Value(jobject l)  { val.l = l; }
+
+    jvalue val;
+};
+
+} // namespace detail
+
+using namespace detail;
+
+// Base class for Method<>, Field<>, and Constructor<>.
+class Accessor
+{
+    static void GetNsresult(JNIEnv* env, nsresult* rv)
+    {
+        if (env->ExceptionCheck()) {
+#ifdef MOZ_CHECK_JNI
+            env->ExceptionDescribe();
+#endif
+            env->ExceptionClear();
+            *rv = NS_ERROR_FAILURE;
+        } else {
+            *rv = NS_OK;
+        }
+    }
+
+protected:
+    // Called after making a JNIEnv call.
+    template<class Traits>
+    static void EndAccess(const typename Traits::Owner::Context& ctx,
+                          nsresult* rv)
+    {
+        if (Traits::exceptionMode == ExceptionMode::ABORT) {
+            MOZ_CATCH_JNI_EXCEPTION(ctx.Env());
+
+        } else if (Traits::exceptionMode == ExceptionMode::NSRESULT) {
+            GetNsresult(ctx.Env(), rv);
+        }
+    }
+};
+
+
+// Member<> is used to call a JNI method given a traits class.
+template<class Traits, typename ReturnType = typename Traits::ReturnType>
+class Method : public Accessor
+{
+    typedef Accessor Base;
+    typedef typename Traits::Owner::Context Context;
+
+protected:
+    static jmethodID sID;
+
+    static void BeginAccess(const Context& ctx)
+    {
+        MOZ_ASSERT_JNI_THREAD(Traits::callingThread);
+        static_assert(Traits::dispatchTarget == DispatchTarget::CURRENT,
+                      "Dispatching not supported for method call");
+
+        if (sID) {
+            return;
+        }
+
+        if (Traits::isStatic) {
+            MOZ_ALWAYS_TRUE(sID = AndroidBridge::GetStaticMethodID(
+                ctx.Env(), ctx.ClassRef(), Traits::name, Traits::signature));
+        } else {
+            MOZ_ALWAYS_TRUE(sID = AndroidBridge::GetMethodID(
+                ctx.Env(), ctx.ClassRef(), Traits::name, Traits::signature));
+        }
+    }
+
+    static void EndAccess(const Context& ctx, nsresult* rv)
+    {
+        return Base::EndAccess<Traits>(ctx, rv);
+    }
+
+public:
+    template<typename... Args>
+    static ReturnType Call(const Context& ctx, nsresult* rv, const Args&... args)
+    {
+        JNIEnv* const env = ctx.Env();
+        BeginAccess(ctx);
+
+        jvalue jargs[] = {
+            Value(TypeAdapter<Args>::FromNative(env, args)).val ...
+        };
+
+        auto result = TypeAdapter<ReturnType>::ToNative(env,
+                Traits::isStatic ?
+                (env->*TypeAdapter<ReturnType>::StaticCall)(
+                        ctx.RawClassRef(), sID, jargs) :
+                (env->*TypeAdapter<ReturnType>::Call)(
+                        ctx.Get(), sID, jargs));
+
+        EndAccess(ctx, rv);
+        return result;
+    }
+};
+
+// Define sID member.
+template<class T, typename R> jmethodID Method<T, R>::sID;
+
+
+// Specialize void because C++ forbids us from
+// using a "void" temporary result variable.
+template<class Traits>
+class Method<Traits, void> : public Method<Traits, bool>
+{
+    typedef Method<Traits, bool> Base;
+    typedef typename Traits::Owner::Context Context;
+
+public:
+    template<typename... Args>
+    static void Call(const Context& ctx, nsresult* rv,
+                     const Args&... args)
+    {
+        JNIEnv* const env = ctx.Env();
+        Base::BeginAccess(ctx);
+
+        jvalue jargs[] = {
+            Value(TypeAdapter<Args>::FromNative(env, args)).val ...
+        };
+
+        if (Traits::isStatic) {
+            env->CallStaticVoidMethodA(ctx.RawClassRef(), Base::sID, jargs);
+        } else {
+            env->CallVoidMethodA(ctx.Get(), Base::sID, jargs);
+        }
+
+        Base::EndAccess(ctx, rv);
+    }
+};
+
+
+// Constructor<> is used to construct a JNI instance given a traits class.
+template<class Traits>
+class Constructor : protected Method<Traits, typename Traits::ReturnType> {
+    typedef typename Traits::Owner::Context Context;
+    typedef typename Traits::ReturnType ReturnType;
+    typedef Method<Traits, ReturnType> Base;
+
+public:
+    template<typename... Args>
+    static ReturnType Call(const Context& ctx, nsresult* rv,
+                           const Args&... args)
+    {
+        JNIEnv* const env = ctx.Env();
+        Base::BeginAccess(ctx);
+
+        jvalue jargs[] = {
+            Value(TypeAdapter<Args>::FromNative(env, args)).val ...
+        };
+
+        auto result = TypeAdapter<ReturnType>::ToNative(
+                env, env->NewObjectA(ctx.RawClassRef(), Base::sID, jargs));
+
+        Base::EndAccess(ctx, rv);
+        return result;
+    }
+};
+
+
+// Field<> is used to access a JNI field given a traits class.
+template<class Traits>
+class Field : public Accessor
+{
+    typedef Accessor Base;
+    typedef typename Traits::Owner::Context Context;
+    typedef typename Traits::ReturnType GetterType;
+    typedef typename Traits::SetterType SetterType;
+
+private:
+
+    static jfieldID sID;
+
+    static void BeginAccess(const Context& ctx)
+    {
+        MOZ_ASSERT_JNI_THREAD(Traits::callingThread);
+        static_assert(Traits::dispatchTarget == DispatchTarget::CURRENT,
+                      "Dispatching not supported for field access");
+
+        if (sID) {
+            return;
+        }
+
+        if (Traits::isStatic) {
+            MOZ_ALWAYS_TRUE(sID = AndroidBridge::GetStaticFieldID(
+                ctx.Env(), ctx.ClassRef(), Traits::name, Traits::signature));
+        } else {
+            MOZ_ALWAYS_TRUE(sID = AndroidBridge::GetFieldID(
+                ctx.Env(), ctx.ClassRef(), Traits::name, Traits::signature));
+        }
+    }
+
+    static void EndAccess(const Context& ctx, nsresult* rv)
+    {
+        return Base::EndAccess<Traits>(ctx, rv);
+    }
+
+public:
+    static GetterType Get(const Context& ctx, nsresult* rv)
+    {
+        JNIEnv* const env = ctx.Env();
+        BeginAccess(ctx);
+
+        auto result = TypeAdapter<GetterType>::ToNative(
+                env, Traits::isStatic ?
+
+                (env->*TypeAdapter<GetterType>::StaticGet)
+                        (ctx.RawClassRef(), sID) :
+
+                (env->*TypeAdapter<GetterType>::Get)
+                        (ctx.Get(), sID));
+
+        EndAccess(ctx, rv);
+        return result;
+    }
+
+    static void Set(const Context& ctx, nsresult* rv, SetterType val)
+    {
+        JNIEnv* const env = ctx.Env();
+        BeginAccess(ctx);
+
+        if (Traits::isStatic) {
+            (env->*TypeAdapter<SetterType>::StaticSet)(
+                    ctx.RawClassRef(), sID,
+                    TypeAdapter<SetterType>::FromNative(env, val));
+        } else {
+            (env->*TypeAdapter<SetterType>::Set)(
+                    ctx.Get(), sID,
+                    TypeAdapter<SetterType>::FromNative(env, val));
+        }
+
+        EndAccess(ctx, rv);
+    }
+};
+
+// Define sID member.
+template<class T> jfieldID Field<T>::sID;
+
+
+// Define the sClassRef member declared in Refs.h and
+// used by Method and Field above.
+template<class C, typename T> jclass Context<C, T>::sClassRef;
+
+} // namespace jni
+} // namespace mozilla
+
+#endif // mozilla_jni_Accessors_h__
diff --git a/widget/android/jni/Natives.h b/widget/android/jni/Natives.h
new file mode 100644
index 0000000000..511d96a87d
--- /dev/null
+++ b/widget/android/jni/Natives.h
@@ -0,0 +1,707 @@
+#ifndef mozilla_jni_Natives_h__
+#define mozilla_jni_Natives_h__
+
+#include <jni.h>
+
+#include "mozilla/IndexSequence.h"
+#include "mozilla/Move.h"
+#include "mozilla/Tuple.h"
+#include "mozilla/TypeTraits.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/WeakPtr.h"
+#include "mozilla/Unused.h"
+#include "mozilla/jni/Accessors.h"
+#include "mozilla/jni/Refs.h"
+#include "mozilla/jni/Types.h"
+#include "mozilla/jni/Utils.h"
+
+namespace mozilla {
+namespace jni {
+
+/**
+ * C++ classes implementing instance (non-static) native methods can choose
+ * from one of two ownership models, when associating a C++ object with a Java
+ * instance.
+ *
+ * * If the C++ class inherits from mozilla::SupportsWeakPtr, weak pointers
+ *   will be used. The Java instance will store and own the pointer to a
+ *   WeakPtr object. The C++ class itself is otherwise not owned or directly
+ *   referenced. To attach a Java instance to a C++ instance, pass in a pointer
+ *   to the C++ class (i.e. MyClass*).
+ *
+ *   class MyClass : public SupportsWeakPtr<MyClass>
+ *                 , public MyJavaClass::Natives<MyClass>
+ *   {
+ *       // ...
+ *
+ *   public:
+ *       MOZ_DECLARE_WEAKREFERENCE_TYPENAME(MyClass)
+ *       using MyJavaClass::Natives<MyClass>::Dispose;
+ *
+ *       void AttachTo(const MyJavaClass::LocalRef& instance)
+ *       {
+ *           MyJavaClass::Natives<MyClass>::AttachInstance(instance, this);
+ *
+ *           // "instance" does NOT own "this", so the C++ object
+ *           // lifetime is separate from the Java object lifetime.
+ *       }
+ *   };
+ *
+ * * If the C++ class doesn't inherit from mozilla::SupportsWeakPtr, the Java
+ *   instance will store and own a pointer to the C++ object itself. This
+ *   pointer must not be stored or deleted elsewhere. To attach a Java instance
+ *   to a C++ instance, pass in a reference to a UniquePtr of the C++ class
+ *   (i.e. UniquePtr<MyClass>).
+ *
+ *   class MyClass : public MyJavaClass::Natives<MyClass>
+ *   {
+ *       // ...
+ *
+ *   public:
+ *       using MyJavaClass::Natives<MyClass>::Dispose;
+ *
+ *       static void AttachTo(const MyJavaClass::LocalRef& instance)
+ *       {
+ *           MyJavaClass::Natives<MyClass>::AttachInstance(
+ *                   instance, mozilla::MakeUnique<MyClass>());
+ *
+ *           // "instance" owns the newly created C++ object, so the C++
+ *           // object is destroyed as soon as instance.dispose() is called.
+ *       }
+ *   };
+ */
+
+namespace detail {
+
+inline uintptr_t CheckNativeHandle(JNIEnv* env, uintptr_t handle)
+{
+    if (!handle) {
+        if (!env->ExceptionCheck()) {
+            ThrowException(env, "java/lang/NullPointerException",
+                           "Null native pointer");
+        }
+        return 0;
+    }
+    return handle;
+}
+
+template<class Impl, bool UseWeakPtr = mozilla::IsBaseOf<
+                         SupportsWeakPtr<Impl>, Impl>::value /* = false */>
+struct NativePtr
+{
+    static Impl* Get(JNIEnv* env, jobject instance)
+    {
+        return reinterpret_cast<Impl*>(CheckNativeHandle(
+                env, GetNativeHandle(env, instance)));
+    }
+
+    template<class LocalRef>
+    static Impl* Get(const LocalRef& instance)
+    {
+        return Get(instance.Env(), instance.Get());
+    }
+
+    template<class LocalRef>
+    static void Set(const LocalRef& instance, UniquePtr<Impl>&& ptr)
+    {
+        Clear(instance);
+        SetNativeHandle(instance.Env(), instance.Get(),
+                          reinterpret_cast<uintptr_t>(ptr.release()));
+        MOZ_CATCH_JNI_EXCEPTION(instance.Env());
+    }
+
+    template<class LocalRef>
+    static void Clear(const LocalRef& instance)
+    {
+        UniquePtr<Impl> ptr(reinterpret_cast<Impl*>(
+                GetNativeHandle(instance.Env(), instance.Get())));
+        MOZ_CATCH_JNI_EXCEPTION(instance.Env());
+
+        if (ptr) {
+            SetNativeHandle(instance.Env(), instance.Get(), 0);
+            MOZ_CATCH_JNI_EXCEPTION(instance.Env());
+        }
+    }
+};
+
+template<class Impl>
+struct NativePtr<Impl, /* UseWeakPtr = */ true>
+{
+    static Impl* Get(JNIEnv* env, jobject instance)
+    {
+        const auto ptr = reinterpret_cast<WeakPtr<Impl>*>(
+                CheckNativeHandle(env, GetNativeHandle(env, instance)));
+        if (!ptr) {
+            return nullptr;
+        }
+
+        Impl* const impl = *ptr;
+        if (!impl) {
+            ThrowException(env, "java/lang/NullPointerException",
+                           "Native object already released");
+        }
+        return impl;
+    }
+
+    template<class LocalRef>
+    static Impl* Get(const LocalRef& instance)
+    {
+        return Get(instance.Env(), instance.Get());
+    }
+
+    template<class LocalRef>
+    static void Set(const LocalRef& instance, Impl* ptr)
+    {
+        Clear(instance);
+        SetNativeHandle(instance.Env(), instance.Get(),
+                          reinterpret_cast<uintptr_t>(new WeakPtr<Impl>(ptr)));
+        MOZ_CATCH_JNI_EXCEPTION(instance.Env());
+    }
+
+    template<class LocalRef>
+    static void Clear(const LocalRef& instance)
+    {
+        const auto ptr = reinterpret_cast<WeakPtr<Impl>*>(
+                GetNativeHandle(instance.Env(), instance.Get()));
+        MOZ_CATCH_JNI_EXCEPTION(instance.Env());
+
+        if (ptr) {
+            SetNativeHandle(instance.Env(), instance.Get(), 0);
+            MOZ_CATCH_JNI_EXCEPTION(instance.Env());
+            delete ptr;
+        }
+    }
+};
+
+} // namespace detail
+
+using namespace detail;
+
+/**
+ * For JNI native methods that are dispatched to a proxy, i.e. using
+ * @WrapForJNI(dispatchTo = "proxy"), the implementing C++ class must provide a
+ * OnNativeCall member. Subsequently, every native call is automatically
+ * wrapped in a functor object, and the object is passed to OnNativeCall. The
+ * OnNativeCall implementation can choose to invoke the call, save it, dispatch
+ * it to a different thread, etc. Each copy of functor may only be invoked
+ * once.
+ *
+ * class MyClass : public MyJavaClass::Natives<MyClass>
+ * {
+ *     // ...
+ *
+ *     template<class Functor>
+ *     class ProxyRunnable final : public Runnable
+ *     {
+ *         Functor mCall;
+ *     public:
+ *         ProxyRunnable(Functor&& call) : mCall(mozilla::Move(call)) {}
+ *         virtual void run() override { mCall(); }
+ *     };
+ *
+ * public:
+ *     template<class Functor>
+ *     static void OnNativeCall(Functor&& call)
+ *     {
+ *         RunOnAnotherThread(new ProxyRunnable(mozilla::Move(call)));
+ *     }
+ * };
+ */
+
+namespace detail {
+
+// ProxyArg is used to handle JNI ref arguments for proxies. Because a proxied
+// call may happen outside of the original JNI native call, we must save all
+// JNI ref arguments as global refs to avoid the arguments going out of scope.
+template<typename T>
+struct ProxyArg
+{
+    static_assert(mozilla::IsPod<T>::value, "T must be primitive type");
+
+    // Primitive types can be saved by value.
+    typedef T Type;
+    typedef typename TypeAdapter<T>::JNIType JNIType;
+
+    static void Clear(JNIEnv* env, Type&) {}
+
+    static Type From(JNIEnv* env, JNIType val)
+    {
+        return TypeAdapter<T>::ToNative(env, val);
+    }
+};
+
+template<class C, typename T>
+struct ProxyArg<Ref<C, T>>
+{
+    // Ref types need to be saved by global ref.
+    typedef typename C::GlobalRef Type;
+    typedef typename TypeAdapter<Ref<C, T>>::JNIType JNIType;
+
+    static void Clear(JNIEnv* env, Type& ref) { ref.Clear(env); }
+
+    static Type From(JNIEnv* env, JNIType val)
+    {
+        return Type(env, C::Ref::From(val));
+    }
+};
+
+template<typename C> struct ProxyArg<const C&> : ProxyArg<C> {};
+template<> struct ProxyArg<StringParam> : ProxyArg<String::Ref> {};
+template<class C> struct ProxyArg<LocalRef<C>> : ProxyArg<typename C::Ref> {};
+
+// ProxyNativeCall implements the functor object that is passed to OnNativeCall
+template<class Impl, class Owner, bool IsStatic,
+         bool HasThisArg /* has instance/class local ref in the call */,
+         typename... Args>
+class ProxyNativeCall : public AbstractCall
+{
+    // "this arg" refers to the Class::LocalRef (for static methods) or
+    // Owner::LocalRef (for instance methods) that we optionally (as indicated
+    // by HasThisArg) pass into the destination C++ function.
+    typedef typename mozilla::Conditional<IsStatic,
+            Class, Owner>::Type ThisArgClass;
+    typedef typename mozilla::Conditional<IsStatic,
+            jclass, jobject>::Type ThisArgJNIType;
+
+    // Type signature of the destination C++ function, which matches the
+    // Method template parameter in NativeStubImpl::Wrap.
+    typedef typename mozilla::Conditional<IsStatic,
+            typename mozilla::Conditional<HasThisArg,
+                    void (*) (const Class::LocalRef&, Args...),
+                    void (*) (Args...)>::Type,
+            typename mozilla::Conditional<HasThisArg,
+                    void (Impl::*) (const typename Owner::LocalRef&, Args...),
+                    void (Impl::*) (Args...)>::Type>::Type NativeCallType;
+
+    // Destination C++ function.
+    NativeCallType mNativeCall;
+    // Saved this arg.
+    typename ThisArgClass::GlobalRef mThisArg;
+    // Saved arguments.
+    mozilla::Tuple<typename ProxyArg<Args>::Type...> mArgs;
+
+    // We cannot use IsStatic and HasThisArg directly (without going through
+    // extra hoops) because GCC complains about invalid overloads, so we use
+    // another pair of template parameters, Static and ThisArg.
+
+    template<bool Static, bool ThisArg, size_t... Indices>
+    typename mozilla::EnableIf<Static && ThisArg, void>::Type
+    Call(const Class::LocalRef& cls,
+         mozilla::IndexSequence<Indices...>) const
+    {
+        (*mNativeCall)(cls, mozilla::Get<Indices>(mArgs)...);
+    }
+
+    template<bool Static, bool ThisArg, size_t... Indices>
+    typename mozilla::EnableIf<Static && !ThisArg, void>::Type
+    Call(const Class::LocalRef& cls,
+         mozilla::IndexSequence<Indices...>) const
+    {
+        (*mNativeCall)(mozilla::Get<Indices>(mArgs)...);
+    }
+
+    template<bool Static, bool ThisArg, size_t... Indices>
+    typename mozilla::EnableIf<!Static && ThisArg, void>::Type
+    Call(const typename Owner::LocalRef& inst,
+         mozilla::IndexSequence<Indices...>) const
+    {
+        Impl* const impl = NativePtr<Impl>::Get(inst);
+        MOZ_CATCH_JNI_EXCEPTION(inst.Env());
+        (impl->*mNativeCall)(inst, mozilla::Get<Indices>(mArgs)...);
+    }
+
+    template<bool Static, bool ThisArg, size_t... Indices>
+    typename mozilla::EnableIf<!Static && !ThisArg, void>::Type
+    Call(const typename Owner::LocalRef& inst,
+         mozilla::IndexSequence<Indices...>) const
+    {
+        Impl* const impl = NativePtr<Impl>::Get(inst);
+        MOZ_CATCH_JNI_EXCEPTION(inst.Env());
+        (impl->*mNativeCall)(mozilla::Get<Indices>(mArgs)...);
+    }
+
+    template<size_t... Indices>
+    void Clear(JNIEnv* env, mozilla::IndexSequence<Indices...>)
+    {
+        int dummy[] = {
+            (ProxyArg<Args>::Clear(env, Get<Indices>(mArgs)), 0)...
+        };
+        mozilla::Unused << dummy;
+    }
+
+public:
+    // The class that implements the call target.
+    typedef Impl TargetClass;
+    typedef typename ThisArgClass::Param ThisArgType;
+
+    static const bool isStatic = IsStatic;
+
+    ProxyNativeCall(ThisArgJNIType thisArg,
+                    NativeCallType nativeCall,
+                    JNIEnv* env,
+                    typename ProxyArg<Args>::JNIType... args)
+        : mNativeCall(nativeCall)
+        , mThisArg(env, ThisArgClass::Ref::From(thisArg))
+        , mArgs(ProxyArg<Args>::From(env, args)...)
+    {}
+
+    ProxyNativeCall(ProxyNativeCall&&) = default;
+    ProxyNativeCall(const ProxyNativeCall&) = default;
+
+    // Get class ref for static calls or object ref for instance calls.
+    typename ThisArgClass::Param GetThisArg() const { return mThisArg; }
+
+    // Return if target is the given function pointer / pointer-to-member.
+    // Because we can only compare pointers of the same type, we use a
+    // templated overload that is chosen only if given a different type of
+    // pointer than our target pointer type.
+    bool IsTarget(NativeCallType call) const { return call == mNativeCall; }
+    template<typename T> bool IsTarget(T&&) const { return false; }
+
+    // Redirect the call to another function / class member with the same
+    // signature as the original target. Crash if given a wrong signature.
+    void SetTarget(NativeCallType call) { mNativeCall = call; }
+    template<typename T> void SetTarget(T&&) const { MOZ_CRASH(); }
+
+    void operator()() override
+    {
+        JNIEnv* const env = GetEnvForThread();
+        typename ThisArgClass::LocalRef thisArg(env, mThisArg);
+        Call<IsStatic, HasThisArg>(
+                thisArg, typename IndexSequenceFor<Args...>::Type());
+
+        // Clear all saved global refs. We do this after the call is invoked,
+        // and not inside the destructor because we already have a JNIEnv here,
+        // so it's more efficient to clear out the saved args here. The
+        // downside is that the call can only be invoked once.
+        Clear(env, typename IndexSequenceFor<Args...>::Type());
+        mThisArg.Clear(env);
+    }
+};
+
+template<class Impl, bool HasThisArg, typename... Args>
+struct Dispatcher
+{
+    template<class Traits, bool IsStatic = Traits::isStatic,
+             typename... ProxyArgs>
+    static typename EnableIf<
+            Traits::dispatchTarget == DispatchTarget::PROXY, void>::Type
+    Run(ProxyArgs&&... args)
+    {
+        Impl::OnNativeCall(ProxyNativeCall<
+                Impl, typename Traits::Owner, IsStatic,
+                HasThisArg, Args...>(Forward<ProxyArgs>(args)...));
+    }
+
+    template<class Traits, bool IsStatic = Traits::isStatic,
+             typename ThisArg, typename... ProxyArgs>
+    static typename EnableIf<
+            Traits::dispatchTarget == DispatchTarget::GECKO, void>::Type
+    Run(ThisArg thisArg, ProxyArgs&&... args)
+    {
+        // For a static method, do not forward the "this arg" (i.e. the class
+        // local ref) if the implementation does not request it. This saves us
+        // a pair of calls to add/delete global ref.
+        DispatchToGeckoThread(MakeUnique<ProxyNativeCall<
+                Impl, typename Traits::Owner, IsStatic, HasThisArg,
+                Args...>>(HasThisArg || !IsStatic ? thisArg : nullptr,
+                          Forward<ProxyArgs>(args)...));
+    }
+
+    template<class Traits, bool IsStatic = false, typename... ProxyArgs>
+    static typename EnableIf<
+            Traits::dispatchTarget == DispatchTarget::CURRENT, void>::Type
+    Run(ProxyArgs&&... args) {}
+};
+
+} // namespace detail
+
+// Wrapper methods that convert arguments from the JNI types to the native
+// types, e.g. from jobject to jni::Object::Ref. For instance methods, the
+// wrapper methods also convert calls to calls on objects.
+//
+// We need specialization for static/non-static because the two have different
+// signatures (jobject vs jclass and Impl::*Method vs *Method).
+// We need specialization for return type, because void return type requires
+// us to not deal with the return value.
+
+// Bug 1207642 - Work around Dalvik bug by realigning stack on JNI entry
+#ifdef __i386__
+#define MOZ_JNICALL JNICALL __attribute__((force_align_arg_pointer))
+#else
+#define MOZ_JNICALL JNICALL
+#endif
+
+template<class Traits, class Impl, class Args = typename Traits::Args>
+class NativeStub;
+
+template<class Traits, class Impl, typename... Args>
+class NativeStub<Traits, Impl, jni::Args<Args...>>
+{
+    using Owner = typename Traits::Owner;
+    using ReturnType = typename Traits::ReturnType;
+
+    static constexpr bool isStatic = Traits::isStatic;
+    static constexpr bool isVoid = mozilla::IsVoid<ReturnType>::value;
+
+    struct VoidType { using JNIType = void; };
+    using ReturnJNIType = typename Conditional<
+            isVoid, VoidType, TypeAdapter<ReturnType>>::Type::JNIType;
+
+    using ReturnTypeForNonVoidInstance = typename Conditional<
+            !isStatic && !isVoid, ReturnType, VoidType>::Type;
+    using ReturnTypeForVoidInstance = typename Conditional<
+            !isStatic && isVoid, ReturnType, VoidType&>::Type;
+    using ReturnTypeForNonVoidStatic = typename Conditional<
+            isStatic && !isVoid, ReturnType, VoidType>::Type;
+    using ReturnTypeForVoidStatic = typename Conditional<
+            isStatic && isVoid, ReturnType, VoidType&>::Type;
+
+    static_assert(Traits::dispatchTarget == DispatchTarget::CURRENT || isVoid,
+                  "Dispatched calls must have void return type");
+
+public:
+    // Non-void instance method
+    template<ReturnTypeForNonVoidInstance (Impl::*Method) (Args...)>
+    static MOZ_JNICALL ReturnJNIType
+    Wrap(JNIEnv* env, jobject instance,
+         typename TypeAdapter<Args>::JNIType... args)
+    {
+        MOZ_ASSERT_JNI_THREAD(Traits::callingThread);
+
+        Impl* const impl = NativePtr<Impl>::Get(env, instance);
+        if (!impl) {
+            // There is a pending JNI exception at this point.
+            return ReturnJNIType();
+        }
+        return TypeAdapter<ReturnType>::FromNative(env,
+                (impl->*Method)(TypeAdapter<Args>::ToNative(env, args)...));
+    }
+
+    // Non-void instance method with instance reference
+    template<ReturnTypeForNonVoidInstance (Impl::*Method)
+             (const typename Owner::LocalRef&, Args...)>
+    static MOZ_JNICALL ReturnJNIType
+    Wrap(JNIEnv* env, jobject instance,
+         typename TypeAdapter<Args>::JNIType... args)
+    {
+        MOZ_ASSERT_JNI_THREAD(Traits::callingThread);
+
+        Impl* const impl = NativePtr<Impl>::Get(env, instance);
+        if (!impl) {
+            // There is a pending JNI exception at this point.
+            return ReturnJNIType();
+        }
+        auto self = Owner::LocalRef::Adopt(env, instance);
+        const auto res = TypeAdapter<ReturnType>::FromNative(env,
+                (impl->*Method)(self, TypeAdapter<Args>::ToNative(env, args)...));
+        self.Forget();
+        return res;
+    }
+
+    // Void instance method
+    template<ReturnTypeForVoidInstance (Impl::*Method) (Args...)>
+    static MOZ_JNICALL void
+    Wrap(JNIEnv* env, jobject instance,
+         typename TypeAdapter<Args>::JNIType... args)
+    {
+        MOZ_ASSERT_JNI_THREAD(Traits::callingThread);
+
+        if (Traits::dispatchTarget != DispatchTarget::CURRENT) {
+            Dispatcher<Impl, /* HasThisArg */ false, Args...>::
+                    template Run<Traits>(instance, Method, env, args...);
+            return;
+        }
+
+        Impl* const impl = NativePtr<Impl>::Get(env, instance);
+        if (!impl) {
+            // There is a pending JNI exception at this point.
+            return;
+        }
+        (impl->*Method)(TypeAdapter<Args>::ToNative(env, args)...);
+    }
+
+    // Void instance method with instance reference
+    template<ReturnTypeForVoidInstance (Impl::*Method)
+             (const typename Owner::LocalRef&, Args...)>
+    static MOZ_JNICALL void
+    Wrap(JNIEnv* env, jobject instance,
+         typename TypeAdapter<Args>::JNIType... args)
+    {
+        MOZ_ASSERT_JNI_THREAD(Traits::callingThread);
+
+        if (Traits::dispatchTarget != DispatchTarget::CURRENT) {
+            Dispatcher<Impl, /* HasThisArg */ true, Args...>::
+                    template Run<Traits>(instance, Method, env, args...);
+            return;
+        }
+
+        Impl* const impl = NativePtr<Impl>::Get(env, instance);
+        if (!impl) {
+            // There is a pending JNI exception at this point.
+            return;
+        }
+        auto self = Owner::LocalRef::Adopt(env, instance);
+        (impl->*Method)(self, TypeAdapter<Args>::ToNative(env, args)...);
+        self.Forget();
+    }
+
+    // Overload for DisposeNative
+    template<ReturnTypeForVoidInstance (*DisposeNative)
+             (const typename Owner::LocalRef&)>
+    static MOZ_JNICALL void
+    Wrap(JNIEnv* env, jobject instance)
+    {
+        MOZ_ASSERT_JNI_THREAD(Traits::callingThread);
+
+        if (Traits::dispatchTarget != DispatchTarget::CURRENT) {
+            using LocalRef = typename Owner::LocalRef;
+            Dispatcher<Impl, /* HasThisArg */ false, const LocalRef&>::
+                    template Run<Traits, /* IsStatic */ true>(
+                    /* ThisArg */ nullptr, DisposeNative, env, instance);
+            return;
+        }
+
+        auto self = Owner::LocalRef::Adopt(env, instance);
+        (Impl::DisposeNative)(self);
+        self.Forget();
+    }
+
+    // Non-void static method
+    template<ReturnTypeForNonVoidStatic (*Method) (Args...)>
+    static MOZ_JNICALL ReturnJNIType
+    Wrap(JNIEnv* env, jclass, typename TypeAdapter<Args>::JNIType... args)
+    {
+        MOZ_ASSERT_JNI_THREAD(Traits::callingThread);
+
+        return TypeAdapter<ReturnType>::FromNative(env,
+                (*Method)(TypeAdapter<Args>::ToNative(env, args)...));
+    }
+
+    // Non-void static method with class reference
+    template<ReturnTypeForNonVoidStatic (*Method)
+             (const Class::LocalRef&, Args...)>
+    static MOZ_JNICALL ReturnJNIType
+    Wrap(JNIEnv* env, jclass cls, typename TypeAdapter<Args>::JNIType... args)
+    {
+        MOZ_ASSERT_JNI_THREAD(Traits::callingThread);
+
+        auto clazz = Class::LocalRef::Adopt(env, cls);
+        const auto res = TypeAdapter<ReturnType>::FromNative(env,
+                (*Method)(clazz, TypeAdapter<Args>::ToNative(env, args)...));
+        clazz.Forget();
+        return res;
+    }
+
+    // Void static method
+    template<ReturnTypeForVoidStatic (*Method) (Args...)>
+    static MOZ_JNICALL void
+    Wrap(JNIEnv* env, jclass cls, typename TypeAdapter<Args>::JNIType... args)
+    {
+        MOZ_ASSERT_JNI_THREAD(Traits::callingThread);
+
+        if (Traits::dispatchTarget != DispatchTarget::CURRENT) {
+            Dispatcher<Impl, /* HasThisArg */ false, Args...>::
+                    template Run<Traits>(cls, Method, env, args...);
+            return;
+        }
+
+        (*Method)(TypeAdapter<Args>::ToNative(env, args)...);
+    }
+
+    // Void static method with class reference
+    template<ReturnTypeForVoidStatic (*Method)
+             (const Class::LocalRef&, Args...)>
+    static MOZ_JNICALL void
+    Wrap(JNIEnv* env, jclass cls, typename TypeAdapter<Args>::JNIType... args)
+    {
+        MOZ_ASSERT_JNI_THREAD(Traits::callingThread);
+
+        if (Traits::dispatchTarget != DispatchTarget::CURRENT) {
+            Dispatcher<Impl, /* HasThisArg */ true, Args...>::
+                    template Run<Traits>(cls, Method, env, args...);
+            return;
+        }
+
+        auto clazz = Class::LocalRef::Adopt(env, cls);
+        (*Method)(clazz, TypeAdapter<Args>::ToNative(env, args)...);
+        clazz.Forget();
+    }
+};
+
+// Generate a JNINativeMethod from a native
+// method's traits class and a wrapped stub.
+template<class Traits, typename Ret, typename... Args>
+constexpr JNINativeMethod MakeNativeMethod(MOZ_JNICALL Ret (*stub)(JNIEnv*, Args...))
+{
+    return {
+        Traits::name,
+        Traits::signature,
+        reinterpret_cast<void*>(stub)
+    };
+}
+
+// Class inherited by implementing class.
+template<class Cls, class Impl>
+class NativeImpl
+{
+    typedef typename Cls::template Natives<Impl> Natives;
+
+    static bool sInited;
+
+public:
+    static void Init() {
+        if (sInited) {
+            return;
+        }
+        const auto& ctx = typename Cls::Context();
+        ctx.Env()->RegisterNatives(
+                ctx.ClassRef(), Natives::methods,
+                sizeof(Natives::methods) / sizeof(Natives::methods[0]));
+        MOZ_CATCH_JNI_EXCEPTION(ctx.Env());
+        sInited = true;
+    }
+
+protected:
+
+    // Associate a C++ instance with a Java instance.
+    static void AttachNative(const typename Cls::LocalRef& instance,
+                             SupportsWeakPtr<Impl>* ptr)
+    {
+        static_assert(mozilla::IsBaseOf<SupportsWeakPtr<Impl>, Impl>::value,
+                      "Attach with UniquePtr&& when not using WeakPtr");
+        return NativePtr<Impl>::Set(instance, static_cast<Impl*>(ptr));
+    }
+
+    static void AttachNative(const typename Cls::LocalRef& instance,
+                             UniquePtr<Impl>&& ptr)
+    {
+        static_assert(!mozilla::IsBaseOf<SupportsWeakPtr<Impl>, Impl>::value,
+                      "Attach with SupportsWeakPtr* when using WeakPtr");
+        return NativePtr<Impl>::Set(instance, mozilla::Move(ptr));
+    }
+
+    // Get the C++ instance associated with a Java instance.
+    // There is always a pending exception if the return value is nullptr.
+    static Impl* GetNative(const typename Cls::LocalRef& instance) {
+        return NativePtr<Impl>::Get(instance);
+    }
+
+    static void DisposeNative(const typename Cls::LocalRef& instance) {
+        NativePtr<Impl>::Clear(instance);
+    }
+
+    NativeImpl() {
+        // Initialize on creation if not already initialized.
+        Init();
+    }
+};
+
+// Define static member.
+template<class C, class I>
+bool NativeImpl<C, I>::sInited;
+
+} // namespace jni
+} // namespace mozilla
+
+#endif // mozilla_jni_Natives_h__
diff --git a/widget/android/jni/Refs.h b/widget/android/jni/Refs.h
new file mode 100644
index 0000000000..9f54ee5cd9
--- /dev/null
+++ b/widget/android/jni/Refs.h
@@ -0,0 +1,953 @@
+#ifndef mozilla_jni_Refs_h__
+#define mozilla_jni_Refs_h__
+
+#include <jni.h>
+
+#include "mozilla/Move.h"
+#include "mozilla/jni/Utils.h"
+
+#include "nsError.h" // for nsresult
+#include "nsString.h"
+#include "nsTArray.h"
+
+namespace mozilla {
+namespace jni {
+
+// Wrapped object reference (e.g. jobject, jclass, etc...)
+template<class Cls, typename JNIType> class Ref;
+// Represents a calling context for JNI methods.
+template<class Cls, typename JNIType> class Context;
+// Wrapped local reference that inherits from Ref.
+template<class Cls> class LocalRef;
+// Wrapped global reference that inherits from Ref.
+template<class Cls> class GlobalRef;
+// Wrapped dangling reference that's owned by someone else.
+template<class Cls> class DependentRef;
+
+
+// Class to hold the native types of a method's arguments.
+// For example, if a method has signature (ILjava/lang/String;)V,
+// its arguments class would be jni::Args<int32_t, jni::String::Param>
+template<typename...>
+struct Args {};
+
+
+class Object;
+
+// Base class for Ref and its specializations.
+template<class Cls, typename Type>
+class Ref
+{
+    template<class C, typename T> friend class Ref;
+
+    using Self = Ref<Cls, Type>;
+    using bool_type = void (Self::*)() const;
+    void non_null_reference() const {}
+
+    // A Cls-derivative that allows copying
+    // (e.g. when acting as a return value).
+    struct CopyableCtx : public Context<Cls, Type>
+    {
+        CopyableCtx(JNIEnv* env, Type instance)
+            : Context<Cls, Type>(env, instance)
+        {}
+
+        CopyableCtx(const CopyableCtx& cls)
+            : Context<Cls, Type>(cls.Env(), cls.Get())
+        {}
+    };
+
+    // Private copy constructor so that there's no danger of assigning a
+    // temporary LocalRef/GlobalRef to a Ref, and potentially use the Ref
+    // after the source had been freed.
+    Ref(const Ref&) = default;
+
+protected:
+    static JNIEnv* FindEnv()
+    {
+        return Cls::callingThread == CallingThread::GECKO ?
+                GetGeckoThreadEnv() : GetEnvForThread();
+    }
+
+    Type mInstance;
+
+    // Protected jobject constructor because outside code should be using
+    // Ref::From. Using Ref::From makes it very easy to see which code is using
+    // raw JNI types for future refactoring.
+    explicit Ref(Type instance) : mInstance(instance) {}
+
+public:
+    using JNIType = Type;
+
+    // Construct a Ref form a raw JNI reference.
+    static Ref<Cls, Type> From(JNIType obj)
+    {
+        return Ref<Cls, Type>(obj);
+    }
+
+    // Construct a Ref form a generic object reference.
+    static Ref<Cls, Type> From(const Ref<Object, jobject>& obj)
+    {
+        return Ref<Cls, Type>(JNIType(obj.Get()));
+    }
+
+    MOZ_IMPLICIT Ref(decltype(nullptr)) : mInstance(nullptr) {}
+
+    // Get the raw JNI reference.
+    JNIType Get() const
+    {
+        return mInstance;
+    }
+
+    bool operator==(const Ref& other) const
+    {
+        // Treat two references of the same object as being the same.
+        return mInstance == other.mInstance || JNI_FALSE !=
+                FindEnv()->IsSameObject(mInstance, other.mInstance);
+    }
+
+    bool operator!=(const Ref& other) const
+    {
+        return !operator==(other);
+    }
+
+    bool operator==(decltype(nullptr)) const
+    {
+        return !mInstance;
+    }
+
+    bool operator!=(decltype(nullptr)) const
+    {
+        return !!mInstance;
+    }
+
+    CopyableCtx operator->() const
+    {
+        return CopyableCtx(FindEnv(), mInstance);
+    }
+
+    // Any ref can be cast to an object ref.
+    operator Ref<Object, jobject>() const
+    {
+        return Ref<Object, jobject>(mInstance);
+    }
+
+    // Null checking (e.g. !!ref) using the safe-bool idiom.
+    operator bool_type() const
+    {
+        return mInstance ? &Self::non_null_reference : nullptr;
+    }
+
+    // We don't allow implicit conversion to jobject because that can lead
+    // to easy mistakes such as assigning a temporary LocalRef to a jobject,
+    // and using the jobject after the LocalRef has been freed.
+
+    // We don't allow explicit conversion, to make outside code use Ref::Get.
+    // Using Ref::Get makes it very easy to see which code is using raw JNI
+    // types to make future refactoring easier.
+
+    // operator JNIType() const = delete;
+};
+
+
+// Represents a calling context for JNI methods.
+template<class Cls, typename Type>
+class Context : public Ref<Cls, Type>
+{
+    using Ref = jni::Ref<Cls, Type>;
+
+    static jclass sClassRef; // global reference
+
+protected:
+    JNIEnv* const mEnv;
+
+public:
+    static jclass RawClassRef()
+    {
+        return sClassRef;
+    }
+
+    Context()
+        : Ref(nullptr)
+        , mEnv(Ref::FindEnv())
+    {}
+
+    Context(JNIEnv* env, Type instance)
+        : Ref(instance)
+        , mEnv(env)
+    {}
+
+    jclass ClassRef() const
+    {
+        if (!sClassRef) {
+            const jclass cls = GetClassRef(mEnv, Cls::name);
+            sClassRef = jclass(mEnv->NewGlobalRef(cls));
+            mEnv->DeleteLocalRef(cls);
+        }
+        return sClassRef;
+    }
+
+    JNIEnv* Env() const
+    {
+        return mEnv;
+    }
+
+    bool operator==(const Ref& other) const
+    {
+        // Treat two references of the same object as being the same.
+        return Ref::mInstance == other.mInstance || JNI_FALSE !=
+                mEnv->IsSameObject(Ref::mInstance, other.mInstance);
+    }
+
+    bool operator!=(const Ref& other) const
+    {
+        return !operator==(other);
+    }
+
+    bool operator==(decltype(nullptr)) const
+    {
+        return !Ref::mInstance;
+    }
+
+    bool operator!=(decltype(nullptr)) const
+    {
+        return !!Ref::mInstance;
+    }
+
+    Cls operator->() const
+    {
+        MOZ_ASSERT(Ref::mInstance, "Null jobject");
+        return Cls(*this);
+    }
+};
+
+
+template<class Cls, typename Type = jobject>
+class ObjectBase
+{
+protected:
+    const jni::Context<Cls, Type>& mCtx;
+
+    jclass ClassRef() const { return mCtx.ClassRef(); }
+    JNIEnv* Env() const { return mCtx.Env(); }
+    Type Instance() const { return mCtx.Get(); }
+
+public:
+    using Ref = jni::Ref<Cls, Type>;
+    using Context = jni::Context<Cls, Type>;
+    using LocalRef = jni::LocalRef<Cls>;
+    using GlobalRef = jni::GlobalRef<Cls>;
+    using Param = const Ref&;
+
+    static const CallingThread callingThread = CallingThread::ANY;
+    static const char name[];
+
+    explicit ObjectBase(const Context& ctx) : mCtx(ctx) {}
+
+    Cls* operator->()
+    {
+        return static_cast<Cls*>(this);
+    }
+};
+
+// Binding for a plain jobject.
+class Object : public ObjectBase<Object, jobject>
+{
+public:
+    explicit Object(const Context& ctx) : ObjectBase<Object, jobject>(ctx) {}
+};
+
+// Binding for a built-in object reference other than jobject.
+template<typename T>
+class TypedObject : public ObjectBase<TypedObject<T>, T>
+{
+public:
+    explicit TypedObject(const Context<TypedObject<T>, T>& ctx)
+        : ObjectBase<TypedObject<T>, T>(ctx)
+    {}
+};
+
+
+// Define bindings for built-in types.
+using String = TypedObject<jstring>;
+using Class = TypedObject<jclass>;
+using Throwable = TypedObject<jthrowable>;
+
+using BooleanArray = TypedObject<jbooleanArray>;
+using ByteArray = TypedObject<jbyteArray>;
+using CharArray = TypedObject<jcharArray>;
+using ShortArray = TypedObject<jshortArray>;
+using IntArray = TypedObject<jintArray>;
+using LongArray = TypedObject<jlongArray>;
+using FloatArray = TypedObject<jfloatArray>;
+using DoubleArray = TypedObject<jdoubleArray>;
+using ObjectArray = TypedObject<jobjectArray>;
+
+
+namespace detail {
+
+// See explanation in LocalRef.
+template<class Cls> struct GenericObject { using Type = Object; };
+template<> struct GenericObject<Object>
+{
+    struct Type {
+        using Ref = jni::Ref<Type, jobject>;
+        using Context = jni::Context<Type, jobject>;
+    };
+};
+template<class Cls> struct GenericLocalRef
+{
+    template<class C> struct Type : jni::Object {};
+};
+template<> struct GenericLocalRef<Object>
+{
+    template<class C> using Type = jni::LocalRef<C>;
+};
+
+} // namespace
+
+template<class Cls>
+class LocalRef : public Cls::Context
+{
+    template<class C> friend class LocalRef;
+
+    using Ctx = typename Cls::Context;
+    using Ref = typename Cls::Ref;
+    using JNIType = typename Ref::JNIType;
+
+    // In order to be able to convert LocalRef<Object> to LocalRef<Cls>, we
+    // need constructors and copy assignment operators that take in a
+    // LocalRef<Object> argument. However, if Cls *is* Object, we would have
+    // duplicated constructors and operators with LocalRef<Object> arguments. To
+    // avoid this conflict, we use GenericObject, which is defined as Object for
+    // LocalRef<non-Object> and defined as a dummy class for LocalRef<Object>.
+    using GenericObject = typename detail::GenericObject<Cls>::Type;
+
+    // Similarly, GenericLocalRef is useed to convert LocalRef<Cls> to,
+    // LocalRef<Object>. It's defined as LocalRef<C> for Cls == Object,
+    // and defined as a dummy template class for Cls != Object.
+    template<class C> using GenericLocalRef
+            = typename detail::GenericLocalRef<Cls>::template Type<C>;
+
+    static JNIType NewLocalRef(JNIEnv* env, JNIType obj)
+    {
+        return JNIType(obj ? env->NewLocalRef(obj) : nullptr);
+    }
+
+    LocalRef(JNIEnv* env, JNIType instance) : Ctx(env, instance) {}
+
+    LocalRef& swap(LocalRef& other)
+    {
+        auto instance = other.mInstance;
+        other.mInstance = Ctx::mInstance;
+        Ctx::mInstance = instance;
+        return *this;
+    }
+
+public:
+    // Construct a LocalRef from a raw JNI local reference. Unlike Ref::From,
+    // LocalRef::Adopt returns a LocalRef that will delete the local reference
+    // when going out of scope.
+    static LocalRef Adopt(JNIType instance)
+    {
+        return LocalRef(Ref::FindEnv(), instance);
+    }
+
+    static LocalRef Adopt(JNIEnv* env, JNIType instance)
+    {
+        return LocalRef(env, instance);
+    }
+
+    // Copy constructor.
+    LocalRef(const LocalRef<Cls>& ref)
+        : Ctx(ref.mEnv, NewLocalRef(ref.mEnv, ref.mInstance))
+    {}
+
+    // Move constructor.
+    LocalRef(LocalRef<Cls>&& ref)
+        : Ctx(ref.mEnv, ref.mInstance)
+    {
+        ref.mInstance = nullptr;
+    }
+
+    explicit LocalRef(JNIEnv* env = Ref::FindEnv())
+        : Ctx(env, nullptr)
+    {}
+
+    // Construct a LocalRef from any Ref,
+    // which means creating a new local reference.
+    MOZ_IMPLICIT LocalRef(const Ref& ref)
+        : Ctx(Ref::FindEnv(), nullptr)
+    {
+        Ctx::mInstance = NewLocalRef(Ctx::mEnv, ref.Get());
+    }
+
+    LocalRef(JNIEnv* env, const Ref& ref)
+        : Ctx(env, NewLocalRef(env, ref.Get()))
+    {}
+
+    // Move a LocalRef<Object> into a LocalRef<Cls> without
+    // creating/deleting local references.
+    MOZ_IMPLICIT LocalRef(LocalRef<GenericObject>&& ref)
+        : Ctx(ref.mEnv, JNIType(ref.mInstance))
+    {
+        ref.mInstance = nullptr;
+    }
+
+    template<class C>
+    MOZ_IMPLICIT LocalRef(GenericLocalRef<C>&& ref)
+        : Ctx(ref.mEnv, ref.mInstance)
+    {
+        ref.mInstance = nullptr;
+    }
+
+    // Implicitly converts nullptr to LocalRef.
+    MOZ_IMPLICIT LocalRef(decltype(nullptr))
+        : Ctx(Ref::FindEnv(), nullptr)
+    {}
+
+    ~LocalRef()
+    {
+        if (Ctx::mInstance) {
+            Ctx::mEnv->DeleteLocalRef(Ctx::mInstance);
+            Ctx::mInstance = nullptr;
+        }
+    }
+
+    // Get the raw JNI reference that can be used as a return value.
+    // Returns the same JNI type (jobject, jstring, etc.) as the underlying Ref.
+    typename Ref::JNIType Forget()
+    {
+        const auto obj = Ctx::Get();
+        Ctx::mInstance = nullptr;
+        return obj;
+    }
+
+    LocalRef<Cls>& operator=(LocalRef<Cls> ref)
+    {
+        return swap(ref);
+    }
+
+    LocalRef<Cls>& operator=(const Ref& ref)
+    {
+        LocalRef<Cls> newRef(Ctx::mEnv, ref);
+        return swap(newRef);
+    }
+
+    LocalRef<Cls>& operator=(LocalRef<GenericObject>&& ref)
+    {
+        LocalRef<Cls> newRef(mozilla::Move(ref));
+        return swap(newRef);
+    }
+
+    template<class C>
+    LocalRef<Cls>& operator=(GenericLocalRef<C>&& ref)
+    {
+        LocalRef<Cls> newRef(mozilla::Move(ref));
+        return swap(newRef);
+    }
+
+    LocalRef<Cls>& operator=(decltype(nullptr))
+    {
+        LocalRef<Cls> newRef(Ctx::mEnv, nullptr);
+        return swap(newRef);
+    }
+};
+
+
+template<class Cls>
+class GlobalRef : public Cls::Ref
+{
+    using Ref = typename Cls::Ref;
+    using JNIType = typename Ref::JNIType;
+
+    static JNIType NewGlobalRef(JNIEnv* env, JNIType instance)
+    {
+        return JNIType(instance ? env->NewGlobalRef(instance) : nullptr);
+    }
+
+    GlobalRef& swap(GlobalRef& other)
+    {
+        auto instance = other.mInstance;
+        other.mInstance = Ref::mInstance;
+        Ref::mInstance = instance;
+        return *this;
+    }
+
+public:
+    GlobalRef()
+        : Ref(nullptr)
+    {}
+
+    // Copy constructor
+    GlobalRef(const GlobalRef& ref)
+        : Ref(NewGlobalRef(GetEnvForThread(), ref.mInstance))
+    {}
+
+    // Move constructor
+    GlobalRef(GlobalRef&& ref)
+        : Ref(ref.mInstance)
+    {
+        ref.mInstance = nullptr;
+    }
+
+    MOZ_IMPLICIT GlobalRef(const Ref& ref)
+        : Ref(NewGlobalRef(GetEnvForThread(), ref.Get()))
+    {}
+
+    GlobalRef(JNIEnv* env, const Ref& ref)
+        : Ref(NewGlobalRef(env, ref.Get()))
+    {}
+
+    MOZ_IMPLICIT GlobalRef(const LocalRef<Cls>& ref)
+        : Ref(NewGlobalRef(ref.Env(), ref.Get()))
+    {}
+
+    // Implicitly converts nullptr to GlobalRef.
+    MOZ_IMPLICIT GlobalRef(decltype(nullptr))
+        : Ref(nullptr)
+    {}
+
+    ~GlobalRef()
+    {
+        if (Ref::mInstance) {
+            Clear(GetEnvForThread());
+        }
+    }
+
+    // Get the raw JNI reference that can be used as a return value.
+    // Returns the same JNI type (jobject, jstring, etc.) as the underlying Ref.
+    typename Ref::JNIType Forget()
+    {
+        const auto obj = Ref::Get();
+        Ref::mInstance = nullptr;
+        return obj;
+    }
+
+    void Clear(JNIEnv* env)
+    {
+        if (Ref::mInstance) {
+            env->DeleteGlobalRef(Ref::mInstance);
+            Ref::mInstance = nullptr;
+        }
+    }
+
+    GlobalRef<Cls>& operator=(GlobalRef<Cls> ref)
+    {
+        return swap(ref);
+    }
+
+    GlobalRef<Cls>& operator=(const Ref& ref)
+    {
+        GlobalRef<Cls> newRef(ref);
+        return swap(newRef);
+    }
+
+    GlobalRef<Cls>& operator=(const LocalRef<Cls>& ref)
+    {
+        GlobalRef<Cls> newRef(ref);
+        return swap(newRef);
+    }
+
+    GlobalRef<Cls>& operator=(decltype(nullptr))
+    {
+        GlobalRef<Cls> newRef(nullptr);
+        return swap(newRef);
+    }
+};
+
+
+template<class Cls>
+class DependentRef : public Cls::Ref
+{
+    using Ref = typename Cls::Ref;
+
+public:
+    DependentRef(typename Ref::JNIType instance)
+        : Ref(instance)
+    {}
+
+    DependentRef(const DependentRef& ref)
+        : Ref(ref.Get())
+    {}
+};
+
+
+class StringParam;
+
+template<>
+class TypedObject<jstring> : public ObjectBase<TypedObject<jstring>, jstring>
+{
+    using Base = ObjectBase<TypedObject<jstring>, jstring>;
+
+public:
+    using Param = const StringParam&;
+
+    explicit TypedObject(const Context& ctx) : Base(ctx) {}
+
+    size_t Length() const
+    {
+        const size_t ret = Base::Env()->GetStringLength(Base::Instance());
+        MOZ_CATCH_JNI_EXCEPTION(Base::Env());
+        return ret;
+    }
+
+    nsString ToString() const
+    {
+        const jchar* const str = Base::Env()->GetStringChars(
+                Base::Instance(), nullptr);
+        const jsize len = Base::Env()->GetStringLength(Base::Instance());
+
+        nsString result(reinterpret_cast<const char16_t*>(str), len);
+        Base::Env()->ReleaseStringChars(Base::Instance(), str);
+        return result;
+    }
+
+    nsCString ToCString() const
+    {
+        return NS_ConvertUTF16toUTF8(ToString());
+    }
+
+    // Convert jstring to a nsString.
+    operator nsString() const
+    {
+        return ToString();
+    }
+
+    // Convert jstring to a nsCString.
+    operator nsCString() const
+    {
+        return ToCString();
+    }
+};
+
+// Define a custom parameter type for String,
+// which accepts both String::Ref and nsAString/nsACString
+class StringParam : public String::Ref
+{
+    using Ref = String::Ref;
+
+private:
+    // Not null if we should delete ref on destruction.
+    JNIEnv* const mEnv;
+
+    static jstring GetString(JNIEnv* env, const nsAString& str)
+    {
+        const jstring result = env->NewString(
+                reinterpret_cast<const jchar*>(str.BeginReading()),
+                str.Length());
+        MOZ_CATCH_JNI_EXCEPTION(env);
+        return result;
+    }
+
+public:
+    MOZ_IMPLICIT StringParam(decltype(nullptr))
+        : Ref(nullptr)
+        , mEnv(nullptr)
+    {}
+
+    MOZ_IMPLICIT StringParam(const Ref& ref)
+        : Ref(ref.Get())
+        , mEnv(nullptr)
+    {}
+
+    MOZ_IMPLICIT StringParam(const nsAString& str, JNIEnv* env = Ref::FindEnv())
+        : Ref(GetString(env, str))
+        , mEnv(env)
+    {}
+
+    MOZ_IMPLICIT StringParam(const char16_t* str, JNIEnv* env = Ref::FindEnv())
+        : Ref(GetString(env, nsDependentString(str)))
+        , mEnv(env)
+    {}
+
+    MOZ_IMPLICIT StringParam(const nsACString& str, JNIEnv* env = Ref::FindEnv())
+        : Ref(GetString(env, NS_ConvertUTF8toUTF16(str)))
+        , mEnv(env)
+    {}
+
+    MOZ_IMPLICIT StringParam(const char* str, JNIEnv* env = Ref::FindEnv())
+        : Ref(GetString(env, NS_ConvertUTF8toUTF16(str)))
+        , mEnv(env)
+    {}
+
+    StringParam(StringParam&& other)
+        : Ref(other.Get())
+        , mEnv(other.mEnv)
+    {
+        other.mInstance = nullptr;
+    }
+
+    ~StringParam()
+    {
+        if (mEnv && Get()) {
+            mEnv->DeleteLocalRef(Get());
+        }
+    }
+
+    operator String::LocalRef() const
+    {
+        // We can't return our existing ref because the returned
+        // LocalRef could be freed first, so we need a new local ref.
+        return String::LocalRef(mEnv ? mEnv : Ref::FindEnv(), *this);
+    }
+};
+
+
+namespace detail {
+    template<typename T> struct TypeAdapter;
+}
+
+// Ref specialization for arrays.
+template<typename JNIType, class ElementType>
+class ArrayRefBase : public ObjectBase<TypedObject<JNIType>, JNIType>
+{
+    using Base = ObjectBase<TypedObject<JNIType>, JNIType>;
+
+public:
+    explicit ArrayRefBase(const Context<TypedObject<JNIType>, JNIType>& ctx)
+        : Base(ctx)
+    {}
+
+    static typename Base::LocalRef New(const ElementType* data, size_t length) {
+        using JNIElemType = typename detail::TypeAdapter<ElementType>::JNIType;
+        static_assert(sizeof(ElementType) == sizeof(JNIElemType),
+                      "Size of native type must match size of JNI type");
+        JNIEnv* const jenv = mozilla::jni::GetEnvForThread();
+        auto result =
+            (jenv->*detail::TypeAdapter<ElementType>::NewArray)(length);
+        MOZ_CATCH_JNI_EXCEPTION(jenv);
+        (jenv->*detail::TypeAdapter<ElementType>::SetArray)(
+                result, jsize(0), length,
+                reinterpret_cast<const JNIElemType*>(data));
+        MOZ_CATCH_JNI_EXCEPTION(jenv);
+        return Base::LocalRef::Adopt(jenv, result);
+    }
+
+    size_t Length() const
+    {
+        const size_t ret = Base::Env()->GetArrayLength(Base::Instance());
+        MOZ_CATCH_JNI_EXCEPTION(Base::Env());
+        return ret;
+    }
+
+    ElementType GetElement(size_t index) const
+    {
+        using JNIElemType = typename detail::TypeAdapter<ElementType>::JNIType;
+        static_assert(sizeof(ElementType) == sizeof(JNIElemType),
+                      "Size of native type must match size of JNI type");
+
+        ElementType ret;
+        (Base::Env()->*detail::TypeAdapter<ElementType>::GetArray)(
+                Base::Instance(), jsize(index), 1,
+                reinterpret_cast<JNIElemType*>(&ret));
+        MOZ_CATCH_JNI_EXCEPTION(Base::Env());
+        return ret;
+    }
+
+    nsTArray<ElementType> GetElements() const
+    {
+        using JNIElemType = typename detail::TypeAdapter<ElementType>::JNIType;
+        static_assert(sizeof(ElementType) == sizeof(JNIElemType),
+                      "Size of native type must match size of JNI type");
+
+        const jsize len = size_t(Base::Env()->GetArrayLength(Base::Instance()));
+
+        nsTArray<ElementType> array((size_t(len)));
+        array.SetLength(size_t(len));
+        (Base::Env()->*detail::TypeAdapter<ElementType>::GetArray)(
+                Base::Instance(), 0, len,
+                reinterpret_cast<JNIElemType*>(array.Elements()));
+        return array;
+    }
+
+    ElementType operator[](size_t index) const
+    {
+        return GetElement(index);
+    }
+
+    operator nsTArray<ElementType>() const
+    {
+        return GetElements();
+    }
+};
+
+#define DEFINE_PRIMITIVE_ARRAY_REF(JNIType, ElementType) \
+    template<> \
+    class TypedObject<JNIType> : public ArrayRefBase<JNIType, ElementType> \
+    { \
+    public: \
+        explicit TypedObject(const Context& ctx) \
+            : ArrayRefBase<JNIType, ElementType>(ctx) \
+        {} \
+    }
+
+DEFINE_PRIMITIVE_ARRAY_REF(jbooleanArray, bool);
+DEFINE_PRIMITIVE_ARRAY_REF(jbyteArray,    int8_t);
+DEFINE_PRIMITIVE_ARRAY_REF(jcharArray,    char16_t);
+DEFINE_PRIMITIVE_ARRAY_REF(jshortArray,   int16_t);
+DEFINE_PRIMITIVE_ARRAY_REF(jintArray,     int32_t);
+DEFINE_PRIMITIVE_ARRAY_REF(jlongArray,    int64_t);
+DEFINE_PRIMITIVE_ARRAY_REF(jfloatArray,   float);
+DEFINE_PRIMITIVE_ARRAY_REF(jdoubleArray,  double);
+
+#undef DEFINE_PRIMITIVE_ARRAY_REF
+
+
+class ByteBuffer : public ObjectBase<ByteBuffer, jobject>
+{
+public:
+    explicit ByteBuffer(const Context& ctx)
+        : ObjectBase<ByteBuffer, jobject>(ctx)
+    {}
+
+    static LocalRef New(void* data, size_t capacity)
+    {
+        JNIEnv* const env = GetEnvForThread();
+        const auto ret = LocalRef::Adopt(
+                env, env->NewDirectByteBuffer(data, jlong(capacity)));
+        MOZ_CATCH_JNI_EXCEPTION(env);
+        return ret;
+    }
+
+    void* Address()
+    {
+        void* const ret = Env()->GetDirectBufferAddress(Instance());
+        MOZ_CATCH_JNI_EXCEPTION(Env());
+        return ret;
+    }
+
+    size_t Capacity()
+    {
+        const size_t ret = size_t(Env()->GetDirectBufferCapacity(Instance()));
+        MOZ_CATCH_JNI_EXCEPTION(Env());
+        return ret;
+    }
+};
+
+
+template<>
+class TypedObject<jobjectArray>
+    : public ObjectBase<TypedObject<jobjectArray>, jobjectArray>
+{
+    using Base = ObjectBase<TypedObject<jobjectArray>, jobjectArray>;
+
+public:
+    explicit TypedObject(const Context& ctx) : Base(ctx) {}
+
+    size_t Length() const
+    {
+        const size_t ret = Base::Env()->GetArrayLength(Base::Instance());
+        MOZ_CATCH_JNI_EXCEPTION(Base::Env());
+        return ret;
+    }
+
+    Object::LocalRef GetElement(size_t index) const
+    {
+        auto ret = Object::LocalRef::Adopt(
+                Base::Env(), Base::Env()->GetObjectArrayElement(
+                    Base::Instance(), jsize(index)));
+        MOZ_CATCH_JNI_EXCEPTION(Base::Env());
+        return ret;
+    }
+
+    nsTArray<Object::LocalRef> GetElements() const
+    {
+        const jsize len = size_t(Base::Env()->GetArrayLength(Base::Instance()));
+
+        nsTArray<Object::LocalRef> array((size_t(len)));
+        for (jsize i = 0; i < len; i++) {
+            array.AppendElement(Object::LocalRef::Adopt(
+                    Base::Env(), Base::Env()->GetObjectArrayElement(
+                        Base::Instance(), i)));
+            MOZ_CATCH_JNI_EXCEPTION(Base::Env());
+        }
+        return array;
+    }
+
+    Object::LocalRef operator[](size_t index) const
+    {
+        return GetElement(index);
+    }
+
+    operator nsTArray<Object::LocalRef>() const
+    {
+        return GetElements();
+    }
+
+    void SetElement(size_t index, Object::Param element) const
+    {
+        Base::Env()->SetObjectArrayElement(
+                Base::Instance(), jsize(index), element.Get());
+        MOZ_CATCH_JNI_EXCEPTION(Base::Env());
+    }
+};
+
+
+// Support conversion from LocalRef<T>* to LocalRef<Object>*:
+//   LocalRef<Foo> foo;
+//   Foo::GetFoo(&foo); // error because parameter type is LocalRef<Object>*.
+//   Foo::GetFoo(ReturnTo(&foo)); // OK because ReturnTo converts the argument.
+template<class Cls>
+class ReturnToLocal
+{
+private:
+    LocalRef<Cls>* const localRef;
+    LocalRef<Object> objRef;
+
+public:
+    explicit ReturnToLocal(LocalRef<Cls>* ref) : localRef(ref) {}
+    operator LocalRef<Object>*() { return &objRef; }
+
+    ~ReturnToLocal()
+    {
+        if (objRef) {
+            *localRef = mozilla::Move(objRef);
+        }
+    }
+};
+
+template<class Cls>
+ReturnToLocal<Cls> ReturnTo(LocalRef<Cls>* ref)
+{
+    return ReturnToLocal<Cls>(ref);
+}
+
+
+// Support conversion from GlobalRef<T>* to LocalRef<Object/T>*:
+//   GlobalRef<Foo> foo;
+//   Foo::GetFoo(&foo); // error because parameter type is LocalRef<Foo>*.
+//   Foo::GetFoo(ReturnTo(&foo)); // OK because ReturnTo converts the argument.
+template<class Cls>
+class ReturnToGlobal
+{
+private:
+    GlobalRef<Cls>* const globalRef;
+    LocalRef<Object> objRef;
+    LocalRef<Cls> clsRef;
+
+public:
+    explicit ReturnToGlobal(GlobalRef<Cls>* ref) : globalRef(ref) {}
+    operator LocalRef<Object>*() { return &objRef; }
+    operator LocalRef<Cls>*() { return &clsRef; }
+
+    ~ReturnToGlobal()
+    {
+        if (objRef) {
+            *globalRef = (clsRef = mozilla::Move(objRef));
+        } else if (clsRef) {
+            *globalRef = clsRef;
+        }
+    }
+};
+
+template<class Cls>
+ReturnToGlobal<Cls> ReturnTo(GlobalRef<Cls>* ref)
+{
+    return ReturnToGlobal<Cls>(ref);
+}
+
+} // namespace jni
+} // namespace mozilla
+
+#endif // mozilla_jni_Refs_h__
diff --git a/widget/android/jni/Types.h b/widget/android/jni/Types.h
new file mode 100644
index 0000000000..a083d3e50d
--- /dev/null
+++ b/widget/android/jni/Types.h
@@ -0,0 +1,140 @@
+#ifndef mozilla_jni_Types_h__
+#define mozilla_jni_Types_h__
+
+#include <jni.h>
+
+#include "mozilla/jni/Refs.h"
+
+namespace mozilla {
+namespace jni {
+namespace detail {
+
+// TypeAdapter specializations are the interfaces between native/C++ types such
+// as int32_t and JNI types such as jint. The template parameter T is the native
+// type, and each TypeAdapter specialization can have the following members:
+//
+//  * Call: JNIEnv member pointer for making a method call that returns T.
+//  * StaticCall: JNIEnv member pointer for making a static call that returns T.
+//  * Get: JNIEnv member pointer for getting a field of type T.
+//  * StaticGet: JNIEnv member pointer for getting a static field of type T.
+//  * Set: JNIEnv member pointer for setting a field of type T.
+//  * StaticGet: JNIEnv member pointer for setting a static field of type T.
+//  * ToNative: static function that converts the JNI type to the native type.
+//  * FromNative: static function that converts the native type to the JNI type.
+
+template<typename T> struct TypeAdapter;
+
+
+// TypeAdapter<LocalRef<Cls>> applies when jobject is a return value.
+template<class Cls> struct TypeAdapter<LocalRef<Cls>> {
+    using JNIType = typename Cls::Ref::JNIType;
+
+    static constexpr auto Call = &JNIEnv::CallObjectMethodA;
+    static constexpr auto StaticCall = &JNIEnv::CallStaticObjectMethodA;
+    static constexpr auto Get = &JNIEnv::GetObjectField;
+    static constexpr auto StaticGet = &JNIEnv::GetStaticObjectField;
+
+    // Declare instance as jobject because JNI methods return
+    // jobject even if the return value is really jstring, etc.
+    static LocalRef<Cls> ToNative(JNIEnv* env, jobject instance) {
+        return LocalRef<Cls>::Adopt(env, JNIType(instance));
+    }
+
+    static JNIType FromNative(JNIEnv*, LocalRef<Cls>&& instance) {
+        return instance.Forget();
+    }
+};
+
+// clang is picky about function types, including attributes that modify the calling
+// convention, lining up.  GCC appears to be somewhat less so.
+#ifdef __clang__
+#define MOZ_JNICALL_ABI JNICALL
+#else
+#define MOZ_JNICALL_ABI
+#endif
+
+template<class Cls> constexpr jobject
+    (JNIEnv::*TypeAdapter<LocalRef<Cls>>::Call)(jobject, jmethodID, jvalue*) MOZ_JNICALL_ABI;
+template<class Cls> constexpr jobject
+    (JNIEnv::*TypeAdapter<LocalRef<Cls>>::StaticCall)(jclass, jmethodID, jvalue*) MOZ_JNICALL_ABI;
+template<class Cls> constexpr jobject
+    (JNIEnv::*TypeAdapter<LocalRef<Cls>>::Get)(jobject, jfieldID);
+template<class Cls> constexpr jobject
+    (JNIEnv::*TypeAdapter<LocalRef<Cls>>::StaticGet)(jclass, jfieldID);
+
+
+// TypeAdapter<Ref<Cls>> applies when jobject is a parameter value.
+template<class Cls, typename T> struct TypeAdapter<Ref<Cls, T>> {
+    using JNIType = typename Ref<Cls, T>::JNIType;
+
+    static constexpr auto Set = &JNIEnv::SetObjectField;
+    static constexpr auto StaticSet = &JNIEnv::SetStaticObjectField;
+
+    static DependentRef<Cls> ToNative(JNIEnv* env, JNIType instance) {
+        return DependentRef<Cls>(instance);
+    }
+
+    static JNIType FromNative(JNIEnv*, const Ref<Cls, T>& instance) {
+        return instance.Get();
+    }
+};
+
+template<class Cls, typename T> constexpr void
+    (JNIEnv::*TypeAdapter<Ref<Cls, T>>::Set)(jobject, jfieldID, jobject);
+template<class Cls, typename T> constexpr void
+    (JNIEnv::*TypeAdapter<Ref<Cls, T>>::StaticSet)(jclass, jfieldID, jobject);
+
+
+// jstring has its own Param type.
+template<> struct TypeAdapter<StringParam>
+        : public TypeAdapter<String::Ref>
+{};
+
+template<class Cls> struct TypeAdapter<const Cls&>
+        : public TypeAdapter<Cls>
+{};
+
+
+#define DEFINE_PRIMITIVE_TYPE_ADAPTER(NativeType, JNIType, JNIName) \
+    \
+    template<> struct TypeAdapter<NativeType> { \
+        using JNI##Type = JNIType; \
+    \
+        static constexpr auto Call = &JNIEnv::Call ## JNIName ## MethodA; \
+        static constexpr auto StaticCall = &JNIEnv::CallStatic ## JNIName ## MethodA; \
+        static constexpr auto Get = &JNIEnv::Get ## JNIName ## Field; \
+        static constexpr auto StaticGet = &JNIEnv::GetStatic ## JNIName ## Field; \
+        static constexpr auto Set = &JNIEnv::Set ## JNIName ## Field; \
+        static constexpr auto StaticSet = &JNIEnv::SetStatic ## JNIName ## Field; \
+        static constexpr auto GetArray = &JNIEnv::Get ## JNIName ## ArrayRegion; \
+        static constexpr auto SetArray = &JNIEnv::Set ## JNIName ## ArrayRegion; \
+        static constexpr auto NewArray = &JNIEnv::New ## JNIName ## Array; \
+    \
+        static JNIType FromNative(JNIEnv*, NativeType val) { \
+            return static_cast<JNIType>(val); \
+        } \
+        static NativeType ToNative(JNIEnv*, JNIType val) { \
+            return static_cast<NativeType>(val); \
+        } \
+    }
+
+
+DEFINE_PRIMITIVE_TYPE_ADAPTER(bool,     jboolean, Boolean);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(int8_t,   jbyte,    Byte);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(char16_t, jchar,    Char);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(int16_t,  jshort,   Short);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(int32_t,  jint,     Int);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(int64_t,  jlong,    Long);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(float,    jfloat,   Float);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(double,   jdouble,  Double);
+
+#undef DEFINE_PRIMITIVE_TYPE_ADAPTER
+
+} // namespace detail
+
+using namespace detail;
+
+} // namespace jni
+} // namespace mozilla
+
+#endif // mozilla_jni_Types_h__
diff --git a/widget/android/jni/Utils.cpp b/widget/android/jni/Utils.cpp
new file mode 100644
index 0000000000..145f7e9eab
--- /dev/null
+++ b/widget/android/jni/Utils.cpp
@@ -0,0 +1,301 @@
+#include "Utils.h"
+#include "Types.h"
+
+#include <android/log.h>
+#include <pthread.h>
+
+#include "mozilla/Assertions.h"
+
+#include "GeneratedJNIWrappers.h"
+#include "nsAppShell.h"
+
+#ifdef MOZ_CRASHREPORTER
+#include "nsExceptionHandler.h"
+#endif
+
+namespace mozilla {
+namespace jni {
+
+namespace detail {
+
+#define DEFINE_PRIMITIVE_TYPE_ADAPTER(NativeType, JNIType, JNIName, ABIName) \
+    \
+    constexpr JNIType (JNIEnv::*TypeAdapter<NativeType>::Call) \
+            (jobject, jmethodID, jvalue*) MOZ_JNICALL_ABI; \
+    constexpr JNIType (JNIEnv::*TypeAdapter<NativeType>::StaticCall) \
+            (jclass, jmethodID, jvalue*) MOZ_JNICALL_ABI; \
+    constexpr JNIType (JNIEnv::*TypeAdapter<NativeType>::Get) \
+            (jobject, jfieldID) ABIName; \
+    constexpr JNIType (JNIEnv::*TypeAdapter<NativeType>::StaticGet) \
+            (jclass, jfieldID) ABIName; \
+    constexpr void (JNIEnv::*TypeAdapter<NativeType>::Set) \
+            (jobject, jfieldID, JNIType) ABIName; \
+    constexpr void (JNIEnv::*TypeAdapter<NativeType>::StaticSet) \
+            (jclass, jfieldID, JNIType) ABIName; \
+    constexpr void (JNIEnv::*TypeAdapter<NativeType>::GetArray) \
+            (JNIType ## Array, jsize, jsize, JNIType*)
+
+DEFINE_PRIMITIVE_TYPE_ADAPTER(bool,     jboolean, Boolean, /*nothing*/);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(int8_t,   jbyte,    Byte,    /*nothing*/);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(char16_t, jchar,    Char,    /*nothing*/);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(int16_t,  jshort,   Short,   /*nothing*/);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(int32_t,  jint,     Int,     /*nothing*/);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(int64_t,  jlong,    Long,    /*nothing*/);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(float,    jfloat,   Float,   MOZ_JNICALL_ABI);
+DEFINE_PRIMITIVE_TYPE_ADAPTER(double,   jdouble,  Double,  MOZ_JNICALL_ABI);
+
+#undef DEFINE_PRIMITIVE_TYPE_ADAPTER
+
+} // namespace detail
+
+template<> const char ObjectBase<Object, jobject>::name[] = "java/lang/Object";
+template<> const char ObjectBase<TypedObject<jstring>, jstring>::name[] = "java/lang/String";
+template<> const char ObjectBase<TypedObject<jclass>, jclass>::name[] = "java/lang/Class";
+template<> const char ObjectBase<TypedObject<jthrowable>, jthrowable>::name[] = "java/lang/Throwable";
+template<> const char ObjectBase<TypedObject<jbooleanArray>, jbooleanArray>::name[] = "[Z";
+template<> const char ObjectBase<TypedObject<jbyteArray>, jbyteArray>::name[] = "[B";
+template<> const char ObjectBase<TypedObject<jcharArray>, jcharArray>::name[] = "[C";
+template<> const char ObjectBase<TypedObject<jshortArray>, jshortArray>::name[] = "[S";
+template<> const char ObjectBase<TypedObject<jintArray>, jintArray>::name[] = "[I";
+template<> const char ObjectBase<TypedObject<jlongArray>, jlongArray>::name[] = "[J";
+template<> const char ObjectBase<TypedObject<jfloatArray>, jfloatArray>::name[] = "[F";
+template<> const char ObjectBase<TypedObject<jdoubleArray>, jdoubleArray>::name[] = "[D";
+template<> const char ObjectBase<TypedObject<jobjectArray>, jobjectArray>::name[] = "[Ljava/lang/Object;";
+template<> const char ObjectBase<ByteBuffer, jobject>::name[] = "java/nio/ByteBuffer";
+
+
+JNIEnv* sGeckoThreadEnv;
+
+namespace {
+
+JavaVM* sJavaVM;
+pthread_key_t sThreadEnvKey;
+jclass sOOMErrorClass;
+jobject sClassLoader;
+jmethodID sClassLoaderLoadClass;
+bool sIsFennec;
+
+void UnregisterThreadEnv(void* env)
+{
+    if (!env) {
+        // We were never attached.
+        return;
+    }
+    // The thread may have already been detached. In that case, it's still
+    // okay to call DetachCurrentThread(); it'll simply return an error.
+    // However, we must not access | env | because it may be invalid.
+    MOZ_ASSERT(sJavaVM);
+    sJavaVM->DetachCurrentThread();
+}
+
+} // namespace
+
+void SetGeckoThreadEnv(JNIEnv* aEnv)
+{
+    MOZ_ASSERT(aEnv);
+    MOZ_ASSERT(!sGeckoThreadEnv || sGeckoThreadEnv == aEnv);
+
+    if (!sGeckoThreadEnv
+            && pthread_key_create(&sThreadEnvKey, UnregisterThreadEnv)) {
+        MOZ_CRASH("Failed to initialize required TLS");
+    }
+
+    sGeckoThreadEnv = aEnv;
+    MOZ_ALWAYS_TRUE(!pthread_setspecific(sThreadEnvKey, aEnv));
+
+    MOZ_ALWAYS_TRUE(!aEnv->GetJavaVM(&sJavaVM));
+    MOZ_ASSERT(sJavaVM);
+
+    sOOMErrorClass = Class::GlobalRef(Class::LocalRef::Adopt(
+            aEnv->FindClass("java/lang/OutOfMemoryError"))).Forget();
+    aEnv->ExceptionClear();
+
+    sClassLoader = Object::GlobalRef(java::GeckoThread::ClsLoader()).Forget();
+    sClassLoaderLoadClass = aEnv->GetMethodID(
+            Class::LocalRef::Adopt(aEnv->GetObjectClass(sClassLoader)).Get(),
+            "loadClass", "(Ljava/lang/String;)Ljava/lang/Class;");
+    MOZ_ASSERT(sClassLoader && sClassLoaderLoadClass);
+
+    auto geckoAppClass = Class::LocalRef::Adopt(
+            aEnv->FindClass("org/mozilla/gecko/GeckoApp"));
+    aEnv->ExceptionClear();
+    sIsFennec = !!geckoAppClass;
+}
+
+JNIEnv* GetEnvForThread()
+{
+    MOZ_ASSERT(sGeckoThreadEnv);
+
+    JNIEnv* env = static_cast<JNIEnv*>(pthread_getspecific(sThreadEnvKey));
+    if (env) {
+        return env;
+    }
+
+    // We don't have a saved JNIEnv, so try to get one.
+    // AttachCurrentThread() does the same thing as GetEnv() when a thread is
+    // already attached, so we don't have to call GetEnv() at all.
+    if (!sJavaVM->AttachCurrentThread(&env, nullptr)) {
+        MOZ_ASSERT(env);
+        MOZ_ALWAYS_TRUE(!pthread_setspecific(sThreadEnvKey, env));
+        return env;
+    }
+
+    MOZ_CRASH("Failed to get JNIEnv for thread");
+    return nullptr; // unreachable
+}
+
+bool ThrowException(JNIEnv *aEnv, const char *aClass,
+                    const char *aMessage)
+{
+    MOZ_ASSERT(aEnv, "Invalid thread JNI env");
+
+    Class::LocalRef cls = Class::LocalRef::Adopt(aEnv->FindClass(aClass));
+    MOZ_ASSERT(cls, "Cannot find exception class");
+
+    return !aEnv->ThrowNew(cls.Get(), aMessage);
+}
+
+bool HandleUncaughtException(JNIEnv* aEnv)
+{
+    MOZ_ASSERT(aEnv, "Invalid thread JNI env");
+
+    if (!aEnv->ExceptionCheck()) {
+        return false;
+    }
+
+#ifdef MOZ_CHECK_JNI
+    aEnv->ExceptionDescribe();
+#endif
+
+    Throwable::LocalRef e =
+            Throwable::LocalRef::Adopt(aEnv, aEnv->ExceptionOccurred());
+    MOZ_ASSERT(e);
+    aEnv->ExceptionClear();
+
+    String::LocalRef stack = java::GeckoAppShell::GetExceptionStackTrace(e);
+    if (stack && ReportException(aEnv, e.Get(), stack.Get())) {
+        return true;
+    }
+
+    aEnv->ExceptionClear();
+    java::GeckoAppShell::HandleUncaughtException(e);
+
+    if (NS_WARN_IF(aEnv->ExceptionCheck())) {
+        aEnv->ExceptionDescribe();
+        aEnv->ExceptionClear();
+    }
+
+    return true;
+}
+
+bool ReportException(JNIEnv* aEnv, jthrowable aExc, jstring aStack)
+{
+    bool result = true;
+
+#ifdef MOZ_CRASHREPORTER
+    result &= NS_SUCCEEDED(CrashReporter::AnnotateCrashReport(
+            NS_LITERAL_CSTRING("JavaStackTrace"),
+            String::Ref::From(aStack)->ToCString()));
+#endif // MOZ_CRASHREPORTER
+
+    if (sOOMErrorClass && aEnv->IsInstanceOf(aExc, sOOMErrorClass)) {
+        NS_ABORT_OOM(0); // Unknown OOM size
+    }
+    return result;
+}
+
+namespace {
+
+jclass sJNIObjectClass;
+jfieldID sJNIObjectHandleField;
+
+bool EnsureJNIObject(JNIEnv* env, jobject instance) {
+    if (!sJNIObjectClass) {
+        sJNIObjectClass = Class::GlobalRef(Class::LocalRef::Adopt(GetClassRef(
+                env, "org/mozilla/gecko/mozglue/JNIObject"))).Forget();
+
+        sJNIObjectHandleField = env->GetFieldID(
+                sJNIObjectClass, "mHandle", "J");
+    }
+
+    MOZ_ASSERT(env->IsInstanceOf(instance, sJNIObjectClass));
+    return true;
+}
+
+} // namespace
+
+uintptr_t GetNativeHandle(JNIEnv* env, jobject instance)
+{
+    if (!EnsureJNIObject(env, instance)) {
+        return 0;
+    }
+
+    return static_cast<uintptr_t>(
+            env->GetLongField(instance, sJNIObjectHandleField));
+}
+
+void SetNativeHandle(JNIEnv* env, jobject instance, uintptr_t handle)
+{
+    if (!EnsureJNIObject(env, instance)) {
+        return;
+    }
+
+    env->SetLongField(instance, sJNIObjectHandleField,
+                      static_cast<jlong>(handle));
+}
+
+jclass GetClassRef(JNIEnv* aEnv, const char* aClassName)
+{
+    // First try the default class loader.
+    auto classRef = Class::LocalRef::Adopt(aEnv, aEnv->FindClass(aClassName));
+
+    if (!classRef && sClassLoader) {
+        // If the default class loader failed but we have an app class loader, try that.
+        // Clear the pending exception from failed FindClass call above.
+        aEnv->ExceptionClear();
+        classRef = Class::LocalRef::Adopt(aEnv, jclass(
+                aEnv->CallObjectMethod(sClassLoader, sClassLoaderLoadClass,
+                                       StringParam(aClassName, aEnv).Get())));
+    }
+
+    if (classRef) {
+        return classRef.Forget();
+    }
+
+    __android_log_print(
+            ANDROID_LOG_ERROR, "Gecko",
+            ">>> FATAL JNI ERROR! FindClass(className=\"%s\") failed. "
+            "Did ProGuard optimize away something it shouldn't have?",
+            aClassName);
+    aEnv->ExceptionDescribe();
+    MOZ_CRASH("Cannot find JNI class");
+    return nullptr;
+}
+
+void DispatchToGeckoThread(UniquePtr<AbstractCall>&& aCall)
+{
+    class AbstractCallEvent : public nsAppShell::Event
+    {
+        UniquePtr<AbstractCall> mCall;
+
+    public:
+        AbstractCallEvent(UniquePtr<AbstractCall>&& aCall)
+            : mCall(Move(aCall))
+        {}
+
+        void Run() override
+        {
+            (*mCall)();
+        }
+    };
+
+    nsAppShell::PostEvent(MakeUnique<AbstractCallEvent>(Move(aCall)));
+}
+
+bool IsFennec()
+{
+    return sIsFennec;
+}
+
+} // jni
+} // mozilla
diff --git a/widget/android/jni/Utils.h b/widget/android/jni/Utils.h
new file mode 100644
index 0000000000..38e0b6b0c8
--- /dev/null
+++ b/widget/android/jni/Utils.h
@@ -0,0 +1,147 @@
+#ifndef mozilla_jni_Utils_h__
+#define mozilla_jni_Utils_h__
+
+#include <jni.h>
+
+#include "mozilla/UniquePtr.h"
+
+#if defined(DEBUG) || !defined(RELEASE_OR_BETA)
+#define MOZ_CHECK_JNI
+#endif
+
+#ifdef MOZ_CHECK_JNI
+#include <pthread.h>
+#include "mozilla/Assertions.h"
+#include "APKOpen.h"
+#include "MainThreadUtils.h"
+#endif
+
+namespace mozilla {
+namespace jni {
+
+// How exception during a JNI call should be treated.
+enum class ExceptionMode
+{
+    // Abort on unhandled excepion (default).
+    ABORT,
+    // Ignore the exception and return to caller.
+    IGNORE,
+    // Catch any exception and return a nsresult.
+    NSRESULT,
+};
+
+// Thread that a particular JNI call is allowed on.
+enum class CallingThread
+{
+    // Can be called from any thread (default).
+    ANY,
+    // Can be called from the Gecko thread.
+    GECKO,
+    // Can be called from the Java UI thread.
+    UI,
+};
+
+// If and where a JNI call will be dispatched.
+enum class DispatchTarget
+{
+    // Call happens synchronously on the calling thread (default).
+    CURRENT,
+    // Call happens synchronously on the calling thread, but the call is
+    // wrapped in a function object and is passed thru UsesNativeCallProxy.
+    // Method must return void.
+    PROXY,
+    // Call is dispatched asynchronously on the Gecko thread. Method must
+    // return void.
+    GECKO,
+};
+
+
+extern JNIEnv* sGeckoThreadEnv;
+
+inline bool IsAvailable()
+{
+    return !!sGeckoThreadEnv;
+}
+
+inline JNIEnv* GetGeckoThreadEnv()
+{
+#ifdef MOZ_CHECK_JNI
+    MOZ_RELEASE_ASSERT(NS_IsMainThread(), "Must be on Gecko thread");
+    MOZ_RELEASE_ASSERT(sGeckoThreadEnv, "Must have a JNIEnv");
+#endif
+    return sGeckoThreadEnv;
+}
+
+void SetGeckoThreadEnv(JNIEnv* aEnv);
+
+JNIEnv* GetEnvForThread();
+
+#ifdef MOZ_CHECK_JNI
+#define MOZ_ASSERT_JNI_THREAD(thread) \
+    do { \
+        if ((thread) == mozilla::jni::CallingThread::GECKO) { \
+            MOZ_RELEASE_ASSERT(::NS_IsMainThread()); \
+        } else if ((thread) == mozilla::jni::CallingThread::UI) { \
+            const bool isOnUiThread = ::pthread_equal(::pthread_self(), \
+                                                      ::getJavaUiThread()); \
+            MOZ_RELEASE_ASSERT(isOnUiThread); \
+        } \
+    } while (0)
+#else
+#define MOZ_ASSERT_JNI_THREAD(thread) do {} while (0)
+#endif
+
+bool ThrowException(JNIEnv *aEnv, const char *aClass,
+                    const char *aMessage);
+
+inline bool ThrowException(JNIEnv *aEnv, const char *aMessage)
+{
+    return ThrowException(aEnv, "java/lang/Exception", aMessage);
+}
+
+inline bool ThrowException(const char *aClass, const char *aMessage)
+{
+    return ThrowException(GetEnvForThread(), aClass, aMessage);
+}
+
+inline bool ThrowException(const char *aMessage)
+{
+    return ThrowException(GetEnvForThread(), aMessage);
+}
+
+bool HandleUncaughtException(JNIEnv* aEnv);
+
+bool ReportException(JNIEnv* aEnv, jthrowable aExc, jstring aStack);
+
+#define MOZ_CATCH_JNI_EXCEPTION(env) \
+    do { \
+        if (mozilla::jni::HandleUncaughtException((env))) { \
+            MOZ_CRASH("JNI exception"); \
+        } \
+    } while (0)
+
+
+uintptr_t GetNativeHandle(JNIEnv* env, jobject instance);
+
+void SetNativeHandle(JNIEnv* env, jobject instance, uintptr_t handle);
+
+jclass GetClassRef(JNIEnv* aEnv, const char* aClassName);
+
+struct AbstractCall
+{
+    virtual ~AbstractCall() {}
+    virtual void operator()() = 0;
+};
+
+void DispatchToGeckoThread(UniquePtr<AbstractCall>&& aCall);
+
+/**
+ * Returns whether Gecko is running in a Fennec environment, as determined by
+ * the presence of the GeckoApp class.
+ */
+bool IsFennec();
+
+} // jni
+} // mozilla
+
+#endif // mozilla_jni_Utils_h__
diff --git a/widget/android/jni/moz.build b/widget/android/jni/moz.build
new file mode 100644
index 0000000000..31d7d32e6c
--- /dev/null
+++ b/widget/android/jni/moz.build
@@ -0,0 +1,24 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+EXPORTS.mozilla.jni += [
+    'Accessors.h',
+    'Natives.h',
+    'Refs.h',
+    'Types.h',
+    'Utils.h',
+]
+
+UNIFIED_SOURCES += [
+    'Utils.cpp',
+]
+
+FINAL_LIBRARY = 'xul'
+
+LOCAL_INCLUDES += [
+    '/widget',
+    '/widget/android',
+]