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diff --git a/image/AnimationSurfaceProvider.h b/image/AnimationSurfaceProvider.h
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+++ b/image/AnimationSurfaceProvider.h
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+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+/**
+ * An ISurfaceProvider for animated images.
+ */
+
+#ifndef mozilla_image_AnimationSurfaceProvider_h
+#define mozilla_image_AnimationSurfaceProvider_h
+
+#include "FrameAnimator.h"
+#include "IDecodingTask.h"
+#include "ISurfaceProvider.h"
+
+namespace mozilla {
+namespace image {
+
+/**
+ * An ISurfaceProvider that manages the decoding of animated images and
+ * dynamically generates surfaces for the current playback state of the
+ * animation.
+ */
+class AnimationSurfaceProvider final
+  : public ISurfaceProvider
+  , public IDecodingTask
+{
+public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(AnimationSurfaceProvider, override)
+
+  AnimationSurfaceProvider(NotNull<RasterImage*> aImage,
+                           const SurfaceKey& aSurfaceKey,
+                           NotNull<Decoder*> aDecoder);
+
+
+  //////////////////////////////////////////////////////////////////////////////
+  // ISurfaceProvider implementation.
+  //////////////////////////////////////////////////////////////////////////////
+
+public:
+  // We use the ISurfaceProvider constructor of DrawableSurface to indicate that
+  // our surfaces are computed lazily.
+  DrawableSurface Surface() override { return DrawableSurface(WrapNotNull(this)); }
+
+  bool IsFinished() const override;
+  size_t LogicalSizeInBytes() const override;
+  void AddSizeOfExcludingThis(MallocSizeOf aMallocSizeOf,
+                              size_t& aHeapSizeOut,
+                              size_t& aNonHeapSizeOut) override;
+
+protected:
+  DrawableFrameRef DrawableRef(size_t aFrame) override;
+
+  // Animation frames are always locked. This is because we only want to release
+  // their memory atomically (due to the surface cache discarding them). If they
+  // were unlocked, the OS could end up releasing the memory of random frames
+  // from the middle of the animation, which is not worth the complexity of
+  // dealing with.
+  bool IsLocked() const override { return true; }
+  void SetLocked(bool) override { }
+
+
+  //////////////////////////////////////////////////////////////////////////////
+  // IDecodingTask implementation.
+  //////////////////////////////////////////////////////////////////////////////
+
+public:
+  void Run() override;
+  bool ShouldPreferSyncRun() const override;
+
+  // Full decodes are low priority compared to metadata decodes because they
+  // don't block layout or page load.
+  TaskPriority Priority() const override { return TaskPriority::eLow; }
+
+private:
+  virtual ~AnimationSurfaceProvider();
+
+  void DropImageReference();
+  void CheckForNewFrameAtYield();
+  void CheckForNewFrameAtTerminalState();
+  void AnnounceSurfaceAvailable();
+  void FinishDecoding();
+
+  /// The image associated with our decoder.
+  RefPtr<RasterImage> mImage;
+
+  /// A mutex to protect mDecoder. Always taken before mFramesMutex.
+  mutable Mutex mDecodingMutex;
+
+  /// The decoder used to decode this animation.
+  RefPtr<Decoder> mDecoder;
+
+  /// A mutex to protect mFrames. Always taken after mDecodingMutex.
+  mutable Mutex mFramesMutex;
+
+  /// The frames of this animation, in order.
+  nsTArray<RawAccessFrameRef> mFrames;
+};
+
+} // namespace image
+} // namespace mozilla
+
+#endif // mozilla_image_AnimationSurfaceProvider_h