Add m-esr52 at 52.6.0

1 files changed, 1868 insertions, 0 deletions

diff --git a/layout/base/nsIPresShell.h b/layout/base/nsIPresShell.h
new file mode 100644
index 0000000000..cbbae0e8fd
--- /dev/null
+++ b/layout/base/nsIPresShell.h
@@ -0,0 +1,1868 @@
+/* -*- 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/.
+ *
+ * This Original Code has been modified by IBM Corporation.
+ * Modifications made by IBM described herein are
+ * Copyright (c) International Business Machines
+ * Corporation, 2000
+ *
+ * Modifications to Mozilla code or documentation
+ * identified per MPL Section 3.3
+ *
+ * Date         Modified by     Description of modification
+ * 05/03/2000   IBM Corp.       Observer related defines for reflow
+ */
+
+/* a presentation of a document, part 2 */
+
+#ifndef nsIPresShell_h___
+#define nsIPresShell_h___
+
+#include "mozilla/ArenaObjectID.h"
+#include "mozilla/EventForwards.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/StyleSetHandle.h"
+#include "mozilla/StyleSheet.h"
+#include "mozilla/WeakPtr.h"
+#include "gfxPoint.h"
+#include "nsTHashtable.h"
+#include "nsHashKeys.h"
+#include "nsISupports.h"
+#include "nsIContent.h"
+#include "nsISelectionController.h"
+#include "nsQueryFrame.h"
+#include "nsCoord.h"
+#include "nsColor.h"
+#include "nsFrameManagerBase.h"
+#include "nsRect.h"
+#include "nsRegionFwd.h"
+#include "mozFlushType.h"
+#include "nsWeakReference.h"
+#include <stdio.h> // for FILE definition
+#include "nsChangeHint.h"
+#include "nsRefPtrHashtable.h"
+#include "nsClassHashtable.h"
+#include "nsPresArena.h"
+#include "nsIImageLoadingContent.h"
+#include "nsMargin.h"
+#include "nsFrameState.h"
+#include "Units.h"
+
+#ifdef MOZ_B2G
+#include "nsIHardwareKeyHandler.h"
+#endif
+
+class nsDocShell;
+class nsIDocument;
+class nsIFrame;
+class nsPresContext;
+class nsViewManager;
+class nsView;
+class nsRenderingContext;
+class nsIPageSequenceFrame;
+class nsCanvasFrame;
+class nsAString;
+class nsCaret;
+namespace mozilla {
+class AccessibleCaretEventHub;
+class CSSStyleSheet;
+} // namespace mozilla
+class nsFrameSelection;
+class nsFrameManager;
+class nsILayoutHistoryState;
+class nsIReflowCallback;
+class nsIDOMNode;
+class nsCSSFrameConstructor;
+class nsISelection;
+template<class E> class nsCOMArray;
+class nsWeakFrame;
+class nsIScrollableFrame;
+class gfxContext;
+class nsIDOMEvent;
+class nsDisplayList;
+class nsDisplayListBuilder;
+class nsPIDOMWindowOuter;
+struct nsPoint;
+class nsINode;
+struct nsRect;
+class nsRegion;
+class nsRefreshDriver;
+class nsARefreshObserver;
+class nsAPostRefreshObserver;
+#ifdef ACCESSIBILITY
+class nsAccessibilityService;
+namespace mozilla {
+namespace a11y {
+class DocAccessible;
+} // namespace a11y
+} // namespace mozilla
+#endif
+struct nsArenaMemoryStats;
+class nsITimer;
+
+namespace mozilla {
+class EventStates;
+
+namespace dom {
+class Element;
+class Touch;
+class Selection;
+class ShadowRoot;
+} // namespace dom
+
+namespace layers {
+class LayerManager;
+} // namespace layers
+
+namespace gfx {
+class SourceSurface;
+} // namespace gfx
+} // namespace mozilla
+
+// Flags to pass to SetCapturingContent
+//
+// when assigning capture, ignore whether capture is allowed or not
+#define CAPTURE_IGNOREALLOWED 1
+// true if events should be targeted at the capturing content or its children
+#define CAPTURE_RETARGETTOELEMENT 2
+// true if the current capture wants drags to be prevented
+#define CAPTURE_PREVENTDRAG 4
+// true when the mouse is pointer locked, and events are sent to locked element
+#define CAPTURE_POINTERLOCK 8
+
+typedef struct CapturingContentInfo {
+  // capture should only be allowed during a mousedown event
+  bool mAllowed;
+  bool mPointerLock;
+  bool mRetargetToElement;
+  bool mPreventDrag;
+  mozilla::StaticRefPtr<nsIContent> mContent;
+} CapturingContentInfo;
+
+// a75573d6-34c8-4485-8fb7-edcb6fc70e12
+#define NS_IPRESSHELL_IID \
+{ 0xa75573d6, 0x34c8, 0x4485, \
+  { 0x8f, 0xb7, 0xed, 0xcb, 0x6f, 0xc7, 0x0e, 0x12 } }
+
+// debug VerifyReflow flags
+#define VERIFY_REFLOW_ON                    0x01
+#define VERIFY_REFLOW_NOISY                 0x02
+#define VERIFY_REFLOW_ALL                   0x04
+#define VERIFY_REFLOW_DUMP_COMMANDS         0x08
+#define VERIFY_REFLOW_NOISY_RC              0x10
+#define VERIFY_REFLOW_REALLY_NOISY_RC       0x20
+#define VERIFY_REFLOW_DURING_RESIZE_REFLOW  0x40
+
+#undef NOISY_INTERRUPTIBLE_REFLOW
+
+enum nsRectVisibility {
+  nsRectVisibility_kVisible,
+  nsRectVisibility_kAboveViewport,
+  nsRectVisibility_kBelowViewport,
+  nsRectVisibility_kLeftOfViewport,
+  nsRectVisibility_kRightOfViewport
+};
+
+/**
+ * Presentation shell interface. Presentation shells are the
+ * controlling point for managing the presentation of a document. The
+ * presentation shell holds a live reference to the document, the
+ * presentation context, the style manager, the style set and the root
+ * frame. <p>
+ *
+ * When this object is Release'd, it will release the document, the
+ * presentation context, the style manager, the style set and the root
+ * frame.
+ */
+
+class nsIPresShell : public nsISupports
+{
+public:
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_IPRESSHELL_IID)
+
+protected:
+  typedef mozilla::layers::LayerManager LayerManager;
+  typedef mozilla::gfx::SourceSurface SourceSurface;
+
+  enum eRenderFlag {
+    STATE_IGNORING_VIEWPORT_SCROLLING = 0x1,
+    STATE_DRAWWINDOW_NOT_FLUSHING = 0x2
+  };
+  typedef uint8_t RenderFlags; // for storing the above flags
+
+public:
+  /**
+   * All callers are responsible for calling |Destroy| after calling
+   * |EndObservingDocument|.  It needs to be separate only because form
+   * controls incorrectly store their data in the frames rather than the
+   * content model and printing calls |EndObservingDocument| multiple
+   * times to make form controls behave nicely when printed.
+   */
+  virtual void Destroy() = 0;
+
+  bool IsDestroying() { return mIsDestroying; }
+
+  /**
+   * Make a one-way transition into a "zombie" state.  In this state,
+   * no reflow is done, no painting is done, and no refresh driver
+   * ticks are processed.  This is a dangerous state: it can leave
+   * areas of the composition target unpainted if callers aren't
+   * careful.  (Don't let your zombie presshell out of the shed.)
+   *
+   * This is used in cases where a presshell is created for reasons
+   * other than reflow/painting.
+   */
+  virtual void MakeZombie() = 0;
+
+  /**
+   * All frames owned by the shell are allocated from an arena.  They
+   * are also recycled using free lists.  Separate free lists are
+   * maintained for each frame type (aID), which must always correspond
+   * to the same aSize value.  AllocateFrame returns zero-filled memory.
+   * AllocateFrame is infallible and will abort on out-of-memory.
+   */
+  void* AllocateFrame(nsQueryFrame::FrameIID aID, size_t aSize)
+  {
+    void* result = mFrameArena.AllocateByFrameID(aID, aSize);
+    RecordAlloc(result);
+    memset(result, 0, aSize);
+    return result;
+  }
+
+  void FreeFrame(nsQueryFrame::FrameIID aID, void* aPtr)
+  {
+    RecordFree(aPtr);
+    if (!mIsDestroying)
+      mFrameArena.FreeByFrameID(aID, aPtr);
+  }
+
+  /**
+   * This is for allocating other types of objects (not frames).  Separate free
+   * lists are maintained for each type (aID), which must always correspond to
+   * the same aSize value.  AllocateByObjectID returns zero-filled memory.
+   * AllocateByObjectID is infallible and will abort on out-of-memory.
+   */
+  void* AllocateByObjectID(mozilla::ArenaObjectID aID, size_t aSize)
+  {
+    void* result = mFrameArena.AllocateByObjectID(aID, aSize);
+    RecordAlloc(result);
+    memset(result, 0, aSize);
+    return result;
+  }
+
+  void FreeByObjectID(mozilla::ArenaObjectID aID, void* aPtr)
+  {
+    RecordFree(aPtr);
+    if (!mIsDestroying)
+      mFrameArena.FreeByObjectID(aID, aPtr);
+  }
+
+  /**
+   * Other objects closely related to the frame tree that are allocated
+   * from a separate set of per-size free lists.  Note that different types
+   * of objects that has the same size are allocated from the same list.
+   * AllocateMisc does *not* clear the memory that it returns.
+   * AllocateMisc is infallible and will abort on out-of-memory.
+   *
+   * @deprecated use AllocateByObjectID/FreeByObjectID instead
+   */
+  void* AllocateMisc(size_t aSize)
+  {
+    void* result = mFrameArena.AllocateBySize(aSize);
+    RecordAlloc(result);
+    return result;
+  }
+
+  void FreeMisc(size_t aSize, void* aPtr)
+  {
+    RecordFree(aPtr);
+    if (!mIsDestroying)
+      mFrameArena.FreeBySize(aSize, aPtr);
+  }
+
+  template<typename T>
+  void RegisterArenaRefPtr(mozilla::ArenaRefPtr<T>* aPtr)
+  {
+    mFrameArena.RegisterArenaRefPtr(aPtr);
+  }
+
+  template<typename T>
+  void DeregisterArenaRefPtr(mozilla::ArenaRefPtr<T>* aPtr)
+  {
+    mFrameArena.DeregisterArenaRefPtr(aPtr);
+  }
+
+  void ClearArenaRefPtrs(mozilla::ArenaObjectID aObjectID)
+  {
+    mFrameArena.ClearArenaRefPtrs(aObjectID);
+  }
+
+  nsIDocument* GetDocument() const { return mDocument; }
+
+  nsPresContext* GetPresContext() const { return mPresContext; }
+
+  nsViewManager* GetViewManager() const { return mViewManager; }
+
+  nsRefreshDriver* GetRefreshDriver() const;
+
+#ifdef ACCESSIBILITY
+  /**
+   * Return the document accessible for this pres shell if there is one.
+   */
+  mozilla::a11y::DocAccessible* GetDocAccessible() const
+  {
+    return mDocAccessible;
+  }
+
+  /**
+   * Set the document accessible for this pres shell.
+   */
+  void SetDocAccessible(mozilla::a11y::DocAccessible* aDocAccessible)
+  {
+    mDocAccessible = aDocAccessible;
+  }
+#endif
+
+#ifdef MOZILLA_INTERNAL_API
+  mozilla::StyleSetHandle StyleSet() const { return mStyleSet; }
+
+  nsCSSFrameConstructor* FrameConstructor() const { return mFrameConstructor; }
+
+  nsFrameManager* FrameManager() const {
+    // reinterpret_cast is valid since nsFrameManager does not add
+    // any members over nsFrameManagerBase.
+    return reinterpret_cast<nsFrameManager*>
+                           (const_cast<nsIPresShell*>(this)->mFrameManager);
+  }
+
+#endif
+
+  /* Enable/disable author style level. Disabling author style disables the entire
+   * author level of the cascade, including the HTML preshint level.
+   */
+  // XXX these could easily be inlined, but there is a circular #include
+  // problem with nsStyleSet.
+  void SetAuthorStyleDisabled(bool aDisabled);
+  bool GetAuthorStyleDisabled() const;
+
+  /*
+   * Called when stylesheets are added/removed/enabled/disabled to
+   * recompute style and clear other cached data as needed.  This will
+   * not reconstruct style synchronously; if you need to do that, call
+   * FlushPendingNotifications to flush out style reresolves.
+   *
+   * This handles the the addition and removal of the various types of
+   * style rules that can be in CSS style sheets, such as @font-face
+   * rules and @counter-style rules.
+   *
+   * It requires that StyleSheetAdded, StyleSheetRemoved,
+   * StyleSheetApplicableStateChanged, StyleRuleAdded, StyleRuleRemoved,
+   * or StyleRuleChanged has been called on the style sheets that have
+   * changed.
+   *
+   * // XXXbz why do we have this on the interface anyway?  The only consumer
+   * is calling AddOverrideStyleSheet/RemoveOverrideStyleSheet, and I think
+   * those should just handle reconstructing style data...
+   */
+  void RestyleForCSSRuleChanges();
+
+  /**
+   * Update the style set somehow to take into account changed prefs which
+   * affect document styling.
+   */
+  virtual void UpdatePreferenceStyles() = 0;
+
+  /**
+   * FrameSelection will return the Frame based selection API.
+   * You cannot go back and forth anymore with QI between nsIDOM sel and
+   * nsIFrame sel.
+   */
+  already_AddRefed<nsFrameSelection> FrameSelection();
+
+  /**
+   * ConstFrameSelection returns an object which methods are safe to use for
+   * example in nsIFrame code.
+   */
+  const nsFrameSelection* ConstFrameSelection() const { return mSelection; }
+
+  // Make shell be a document observer.  If called after Destroy() has
+  // been called on the shell, this will be ignored.
+  virtual void BeginObservingDocument() = 0;
+
+  // Make shell stop being a document observer
+  virtual void EndObservingDocument() = 0;
+
+  /**
+   * Return whether Initialize() was previously called.
+   */
+  bool DidInitialize() const { return mDidInitialize; }
+
+  /**
+   * Perform initialization. Constructs the frame for the root content
+   * object and then enqueues a reflow of the frame model into the
+   * specified width and height.
+   *
+   * The coordinates for aWidth and aHeight must be in standard nscoords.
+   *
+   * Callers of this method must hold a reference to this shell that
+   * is guaranteed to survive through arbitrary script execution.
+   * Calling Initialize can execute arbitrary script.
+   */
+  virtual nsresult Initialize(nscoord aWidth, nscoord aHeight) = 0;
+
+  /**
+   * Reflow the frame model into a new width and height.  The
+   * coordinates for aWidth and aHeight must be in standard nscoord's.
+   */
+  virtual nsresult ResizeReflow(nscoord aWidth, nscoord aHeight, nscoord aOldWidth = 0, nscoord aOldHeight = 0) = 0;
+  /**
+   * Do the same thing as ResizeReflow but even if ResizeReflowOverride was
+   * called previously.
+   */
+  virtual nsresult ResizeReflowIgnoreOverride(nscoord aWidth, nscoord aHeight, nscoord aOldWidth, nscoord aOldHeight) = 0;
+
+  /**
+   * Returns true if ResizeReflowOverride has been called.
+   */
+  virtual bool GetIsViewportOverridden() = 0;
+
+  /**
+   * Return true if the presshell expects layout flush.
+   */
+  virtual bool IsLayoutFlushObserver() = 0;
+
+  /**
+   * Called when document load completes.
+   */
+  virtual void LoadComplete() = 0;
+
+  /**
+   * This calls through to the frame manager to get the root frame.
+   */
+  virtual nsIFrame* GetRootFrameExternal() const;
+  nsIFrame* GetRootFrame() const {
+#ifdef MOZILLA_INTERNAL_API
+    return mFrameManager->GetRootFrame();
+#else
+    return GetRootFrameExternal();
+#endif
+  }
+
+  /*
+   * Get root scroll frame from FrameManager()->GetRootFrame().
+   */
+  nsIFrame* GetRootScrollFrame() const;
+
+  /*
+   * The same as GetRootScrollFrame, but returns an nsIScrollableFrame
+   */
+  nsIScrollableFrame* GetRootScrollFrameAsScrollable() const;
+
+  /*
+   * The same as GetRootScrollFrame, but returns an nsIScrollableFrame.
+   * Can be called by code not linked into gklayout.
+   */
+  virtual nsIScrollableFrame* GetRootScrollFrameAsScrollableExternal() const;
+
+  /*
+   * Gets nearest scrollable frame from current focused content or DOM
+   * selection if there is no focused content. The frame is scrollable with
+   * overflow:scroll or overflow:auto in some direction when aDirection is
+   * eEither.  Otherwise, this returns a nearest frame that is scrollable in
+   * the specified direction.
+   */
+  enum ScrollDirection { eHorizontal, eVertical, eEither };
+  nsIScrollableFrame* GetFrameToScrollAsScrollable(ScrollDirection aDirection);
+
+  /**
+   * Returns the page sequence frame associated with the frame hierarchy.
+   * Returns nullptr if not a paginated view.
+   */
+  virtual nsIPageSequenceFrame* GetPageSequenceFrame() const = 0;
+
+  /**
+  * Returns the canvas frame associated with the frame hierarchy.
+  * Returns nullptr if is XUL document.
+  */
+  virtual nsCanvasFrame* GetCanvasFrame() const = 0;
+
+  /**
+   * Gets the placeholder frame associated with the specified frame. This is
+   * a helper frame that forwards the request to the frame manager.
+   */
+  virtual nsIFrame* GetPlaceholderFrameFor(nsIFrame* aFrame) const = 0;
+
+  /**
+   * Tell the pres shell that a frame needs to be marked dirty and needs
+   * Reflow.  It's OK if this is an ancestor of the frame needing reflow as
+   * long as the ancestor chain between them doesn't cross a reflow root.
+   *
+   * The bit to add should be NS_FRAME_IS_DIRTY, NS_FRAME_HAS_DIRTY_CHILDREN
+   * or nsFrameState(0); passing 0 means that dirty bits won't be set on the
+   * frame or its ancestors/descendants, but that intrinsic widths will still
+   * be marked dirty.  Passing aIntrinsicDirty = eResize and aBitToAdd = 0
+   * would result in no work being done, so don't do that.
+   */
+  enum IntrinsicDirty {
+    // XXXldb eResize should be renamed
+    eResize,     // don't mark any intrinsic widths dirty
+    eTreeChange, // mark intrinsic widths dirty on aFrame and its ancestors
+    eStyleChange // Do eTreeChange, plus all of aFrame's descendants
+  };
+  enum ReflowRootHandling {
+    ePositionOrSizeChange, // aFrame is changing position or size
+    eNoPositionOrSizeChange, // ... NOT changing ...
+    eInferFromBitToAdd // is changing iff (aBitToAdd == NS_FRAME_IS_DIRTY)
+
+    // Note:  With eStyleChange, these can also apply to out-of-flows
+    // in addition to aFrame.
+  };
+  virtual void FrameNeedsReflow(nsIFrame *aFrame,
+                                IntrinsicDirty aIntrinsicDirty,
+                                nsFrameState aBitToAdd,
+                                ReflowRootHandling aRootHandling =
+                                  eInferFromBitToAdd) = 0;
+
+  /**
+   * Calls FrameNeedsReflow on all fixed position children of the root frame.
+   */
+  virtual void MarkFixedFramesForReflow(IntrinsicDirty aIntrinsicDirty);
+
+  /**
+   * Tell the presshell that the given frame's reflow was interrupted.  This
+   * will mark as having dirty children a path from the given frame (inclusive)
+   * to the nearest ancestor with a dirty subtree, or to the reflow root
+   * currently being reflowed if no such ancestor exists (inclusive).  This is
+   * to be done immediately after reflow of the current reflow root completes.
+   * This method must only be called during reflow, and the frame it's being
+   * called on must be in the process of being reflowed when it's called.  This
+   * method doesn't mark any intrinsic widths dirty and doesn't add any bits
+   * other than NS_FRAME_HAS_DIRTY_CHILDREN.
+   */
+  virtual void FrameNeedsToContinueReflow(nsIFrame *aFrame) = 0;
+
+  virtual void CancelAllPendingReflows() = 0;
+
+  virtual void NotifyCounterStylesAreDirty() = 0;
+
+  /**
+   * Destroy the frames for aContent.  Note that this may destroy frames
+   * for an ancestor instead - aDestroyedFramesFor contains the content node
+   * where frames were actually destroyed (which should be used in the
+   * CreateFramesFor call).  The frame tree state will be captured before
+   * the frames are destroyed in the frame constructor.
+   */
+  virtual void DestroyFramesFor(nsIContent*  aContent,
+                                nsIContent** aDestroyedFramesFor) = 0;
+  /**
+   * Create new frames for aContent.  It will use the last captured layout
+   * history state captured in the frame constructor to restore the state
+   * in the new frame tree.
+   */
+  virtual void CreateFramesFor(nsIContent* aContent) = 0;
+
+  /**
+   * Recreates the frames for a node
+   */
+  virtual nsresult RecreateFramesFor(nsIContent* aContent) = 0;
+
+  void PostRecreateFramesFor(mozilla::dom::Element* aElement);
+  void RestyleForAnimation(mozilla::dom::Element* aElement,
+                           nsRestyleHint aHint);
+
+  // ShadowRoot has APIs that can change styles so we only
+  // want to restyle elements in the ShadowRoot and not the whole
+  // document.
+  virtual void RecordShadowStyleChange(mozilla::dom::ShadowRoot* aShadowRoot) = 0;
+
+  /**
+   * Determine if it is safe to flush all pending notifications
+   * @param aIsSafeToFlush true if it is safe, false otherwise.
+   *
+   */
+  virtual bool IsSafeToFlush() const = 0;
+
+  /**
+   * Flush pending notifications of the type specified.  This method
+   * will not affect the content model; it'll just affect style and
+   * frames. Callers that actually want up-to-date presentation (other
+   * than the document itself) should probably be calling
+   * nsIDocument::FlushPendingNotifications.
+   *
+   * @param aType the type of notifications to flush
+   */
+  virtual void FlushPendingNotifications(mozFlushType aType) = 0;
+  virtual void FlushPendingNotifications(mozilla::ChangesToFlush aType) = 0;
+
+  /**
+   * Callbacks will be called even if reflow itself fails for
+   * some reason.
+   */
+  virtual nsresult PostReflowCallback(nsIReflowCallback* aCallback) = 0;
+  virtual void CancelReflowCallback(nsIReflowCallback* aCallback) = 0;
+
+  virtual void ClearFrameRefs(nsIFrame* aFrame) = 0;
+
+  /**
+   * Get a reference rendering context. This is a context that should not
+   * be rendered to, but is suitable for measuring text and performing
+   * other non-rendering operations. Guaranteed to return non-null.
+   */
+  virtual already_AddRefed<gfxContext> CreateReferenceRenderingContext() = 0;
+
+  /**
+   * Informs the pres shell that the document is now at the anchor with
+   * the given name.  If |aScroll| is true, scrolls the view of the
+   * document so that the anchor with the specified name is displayed at
+   * the top of the window.  If |aAnchorName| is empty, then this informs
+   * the pres shell that there is no current target, and |aScroll| must
+   * be false.  If |aAdditionalScrollFlags| is nsIPresShell::SCROLL_SMOOTH_AUTO
+   * and |aScroll| is true, the scrolling may be performed with an animation.
+   */
+  virtual nsresult GoToAnchor(const nsAString& aAnchorName, bool aScroll,
+                              uint32_t aAdditionalScrollFlags = 0) = 0;
+
+  /**
+   * Tells the presshell to scroll again to the last anchor scrolled to by
+   * GoToAnchor, if any. This scroll only happens if the scroll
+   * position has not changed since the last GoToAnchor. This is called
+   * by nsDocumentViewer::LoadComplete. This clears the last anchor
+   * scrolled to by GoToAnchor (we don't want to keep it alive if it's
+   * removed from the DOM), so don't call this more than once.
+   */
+  virtual nsresult ScrollToAnchor() = 0;
+
+  enum {
+    SCROLL_TOP     = 0,
+    SCROLL_BOTTOM  = 100,
+    SCROLL_LEFT    = 0,
+    SCROLL_RIGHT   = 100,
+    SCROLL_CENTER  = 50,
+    SCROLL_MINIMUM = -1
+  };
+
+  enum WhenToScroll {
+    SCROLL_ALWAYS,
+    SCROLL_IF_NOT_VISIBLE,
+    SCROLL_IF_NOT_FULLY_VISIBLE
+  };
+  typedef struct ScrollAxis {
+    int16_t mWhereToScroll;
+    WhenToScroll mWhenToScroll : 8;
+    bool mOnlyIfPerceivedScrollableDirection : 1;
+  /**
+   * @param aWhere: Either a percentage or a special value.
+   *                nsIPresShell defines:
+   *                * (Default) SCROLL_MINIMUM = -1: The visible area is
+   *                scrolled to show the entire frame. If the frame is too
+   *                large, the top and left edges are given precedence.
+   *                * SCROLL_TOP = 0: The frame's upper edge is aligned with the
+   *                top edge of the visible area.
+   *                * SCROLL_BOTTOM = 100: The frame's bottom edge is aligned
+   *                with the bottom edge of the visible area.
+   *                * SCROLL_LEFT = 0: The frame's left edge is aligned with the
+   *                left edge of the visible area.
+   *                * SCROLL_RIGHT = 100: The frame's right edge is aligned with
+   *                the right edge of the visible area.
+   *                * SCROLL_CENTER = 50: The frame is centered along the axis
+   *                the ScrollAxis is used for.
+   *
+   *                Other values are treated as a percentage, and the point
+   *                "percent" down the frame is placed at the point "percent"
+   *                down the visible area.
+   * @param aWhen:
+   *                * (Default) SCROLL_IF_NOT_FULLY_VISIBLE: Move the frame only
+   *                if it is not fully visible (including if it's not visible
+   *                at all). Note that in this case if the frame is too large to
+   *                fit in view, it will only be scrolled if more of it can fit
+   *                than is already in view.
+   *                * SCROLL_IF_NOT_VISIBLE: Move the frame only if none of it
+   *                is visible.
+   *                * SCROLL_ALWAYS: Move the frame regardless of its current
+   *                visibility.
+   * @param aOnlyIfPerceivedScrollableDirection:
+   *                If the direction is not a perceived scrollable direction (i.e.
+   *                no scrollbar showing and less than one device pixel of
+   *                scrollable distance), don't scroll. Defaults to false.
+   */
+    explicit ScrollAxis(int16_t aWhere = SCROLL_MINIMUM,
+                        WhenToScroll aWhen = SCROLL_IF_NOT_FULLY_VISIBLE,
+                        bool aOnlyIfPerceivedScrollableDirection = false) :
+      mWhereToScroll(aWhere), mWhenToScroll(aWhen),
+      mOnlyIfPerceivedScrollableDirection(aOnlyIfPerceivedScrollableDirection)
+    {}
+  } ScrollAxis;
+  /**
+   * Scrolls the view of the document so that the primary frame of the content
+   * is displayed in the window. Layout is flushed before scrolling.
+   *
+   * @param aContent  The content object of which primary frame should be
+   *                  scrolled into view.
+   * @param aVertical How to align the frame vertically and when to do so.
+   *                  This is a ScrollAxis of Where and When.
+   * @param aHorizontal How to align the frame horizontally and when to do so.
+   *                  This is a ScrollAxis of Where and When.
+   * @param aFlags    If SCROLL_FIRST_ANCESTOR_ONLY is set, only the nearest
+   *                  scrollable ancestor is scrolled, otherwise all
+   *                  scrollable ancestors may be scrolled if necessary.
+   *                  If SCROLL_OVERFLOW_HIDDEN is set then we may scroll in a
+   *                  direction even if overflow:hidden is specified in that
+   *                  direction; otherwise we will not scroll in that direction
+   *                  when overflow:hidden is set for that direction.
+   *                  If SCROLL_NO_PARENT_FRAMES is set then we only scroll
+   *                  nodes in this document, not in any parent documents which
+   *                  contain this document in a iframe or the like.
+   *                  If SCROLL_SMOOTH is set and CSSOM-VIEW scroll-behavior
+   *                  is enabled, we will scroll smoothly using
+   *                  nsIScrollableFrame::ScrollMode::SMOOTH_MSD; otherwise,
+   *                  nsIScrollableFrame::ScrollMode::INSTANT will be used.
+   *                  If SCROLL_SMOOTH_AUTO is set, the CSSOM-View
+   *                  scroll-behavior attribute is set to 'smooth' on the
+   *                  scroll frame, and CSSOM-VIEW scroll-behavior is enabled,
+   *                  we will scroll smoothly using
+   *                  nsIScrollableFrame::ScrollMode::SMOOTH_MSD; otherwise,
+   *                  nsIScrollableFrame::ScrollMode::INSTANT will be used.
+   */
+  virtual nsresult ScrollContentIntoView(nsIContent* aContent,
+                                                     ScrollAxis  aVertical,
+                                                     ScrollAxis  aHorizontal,
+                                                     uint32_t    aFlags) = 0;
+
+  enum {
+    SCROLL_FIRST_ANCESTOR_ONLY = 0x01,
+    SCROLL_OVERFLOW_HIDDEN = 0x02,
+    SCROLL_NO_PARENT_FRAMES = 0x04,
+    SCROLL_SMOOTH = 0x08,
+    SCROLL_SMOOTH_AUTO = 0x10
+  };
+  /**
+   * Scrolls the view of the document so that the given area of a frame
+   * is visible, if possible. Layout is not flushed before scrolling.
+   *
+   * @param aRect relative to aFrame
+   * @param aVertical see ScrollContentIntoView and ScrollAxis
+   * @param aHorizontal see ScrollContentIntoView and ScrollAxis
+   * @param aFlags if SCROLL_FIRST_ANCESTOR_ONLY is set, only the
+   * nearest scrollable ancestor is scrolled, otherwise all
+   * scrollable ancestors may be scrolled if necessary
+   * if SCROLL_OVERFLOW_HIDDEN is set then we may scroll in a direction
+   * even if overflow:hidden is specified in that direction; otherwise
+   * we will not scroll in that direction when overflow:hidden is
+   * set for that direction
+   * If SCROLL_NO_PARENT_FRAMES is set then we only scroll
+   * nodes in this document, not in any parent documents which
+   * contain this document in a iframe or the like.
+   * @return true if any scrolling happened, false if no scrolling happened
+   */
+  virtual bool ScrollFrameRectIntoView(nsIFrame*     aFrame,
+                                       const nsRect& aRect,
+                                       ScrollAxis    aVertical,
+                                       ScrollAxis    aHorizontal,
+                                       uint32_t      aFlags) = 0;
+
+  /**
+   * Determine if a rectangle specified in the frame's coordinate system
+   * intersects the viewport "enough" to be considered visible.
+   * @param aFrame frame that aRect coordinates are specified relative to
+   * @param aRect rectangle in twips to test for visibility
+   * @param aMinTwips is the minimum distance in from the edge of the viewport
+   *                  that an object must be to be counted visible
+   * @return nsRectVisibility_kVisible if the rect is visible
+   *         nsRectVisibility_kAboveViewport
+   *         nsRectVisibility_kBelowViewport
+   *         nsRectVisibility_kLeftOfViewport
+   *         nsRectVisibility_kRightOfViewport rectangle is outside the viewport
+   *         in the specified direction
+   */
+  virtual nsRectVisibility GetRectVisibility(nsIFrame *aFrame,
+                                             const nsRect &aRect,
+                                             nscoord aMinTwips) const = 0;
+
+  /**
+   * Suppress notification of the frame manager that frames are
+   * being destroyed.
+   */
+  virtual void SetIgnoreFrameDestruction(bool aIgnore) = 0;
+
+  /**
+   * Notification sent by a frame informing the pres shell that it is about to
+   * be destroyed.
+   * This allows any outstanding references to the frame to be cleaned up
+   */
+  virtual void NotifyDestroyingFrame(nsIFrame* aFrame) = 0;
+
+  /**
+   * Get the AccessibleCaretEventHub, if it exists. AddRefs it.
+   */
+  virtual already_AddRefed<mozilla::AccessibleCaretEventHub> GetAccessibleCaretEventHub() const = 0;
+
+  /**
+   * Get the caret, if it exists. AddRefs it.
+   */
+  virtual already_AddRefed<nsCaret> GetCaret() const = 0;
+
+  /**
+   * Set the current caret to a new caret. To undo this, call RestoreCaret.
+   */
+  virtual void SetCaret(nsCaret *aNewCaret) = 0;
+
+  /**
+   * Restore the caret to the original caret that this pres shell was created
+   * with.
+   */
+  virtual void RestoreCaret() = 0;
+
+  /**
+   * Should the images have borders etc.  Actual visual effects are determined
+   * by the frames.  Visual effects may not effect layout, only display.
+   * Takes effect on next repaint, does not force a repaint itself.
+   *
+   * @param aInEnable  if true, visual selection effects are enabled
+   *                   if false visual selection effects are disabled
+   */
+  NS_IMETHOD SetSelectionFlags(int16_t aInEnable) = 0;
+
+  /**
+    * Gets the current state of non text selection effects
+    * @return   current state of non text selection,
+    *           as set by SetDisplayNonTextSelection
+    */
+  int16_t GetSelectionFlags() const { return mSelectionFlags; }
+
+  virtual mozilla::dom::Selection*
+    GetCurrentSelection(mozilla::SelectionType aSelectionType) = 0;
+
+  /**
+   * Gets a selection controller for the focused content in the DOM window
+   * for mDocument.
+   *
+   * @param aFocusedContent     If there is focused content in the DOM window,
+   *                            the focused content will be returned.  This may
+   *                            be nullptr if it's not necessary.
+   * @return                    A selection controller for focused content.
+   *                            E.g., if an <input> element has focus, returns
+   *                            the independent selection controller of it.
+   *                            If the DOM window does not have focused content
+   *                            (similar to Document.activeElement), returns
+   *                            nullptr.
+   */
+  virtual already_AddRefed<nsISelectionController>
+            GetSelectionControllerForFocusedContent(
+              nsIContent** aFocusedContent = nullptr) = 0;
+
+  /**
+    * Interface to dispatch events via the presshell
+    * @note The caller must have a strong reference to the PresShell.
+    */
+  virtual nsresult HandleEventWithTarget(
+                                 mozilla::WidgetEvent* aEvent,
+                                 nsIFrame* aFrame,
+                                 nsIContent* aContent,
+                                 nsEventStatus* aStatus) = 0;
+
+  /**
+   * Dispatch event to content only (NOT full processing)
+   * @note The caller must have a strong reference to the PresShell.
+   */
+  virtual nsresult HandleDOMEventWithTarget(
+                                 nsIContent* aTargetContent,
+                                 mozilla::WidgetEvent* aEvent,
+                                 nsEventStatus* aStatus) = 0;
+
+  /**
+   * Dispatch event to content only (NOT full processing)
+   * @note The caller must have a strong reference to the PresShell.
+   */
+  virtual nsresult HandleDOMEventWithTarget(nsIContent* aTargetContent,
+                                                        nsIDOMEvent* aEvent,
+                                                        nsEventStatus* aStatus) = 0;
+
+  /**
+   * Dispatch AfterKeyboardEvent with specific target.
+   */
+  virtual void DispatchAfterKeyboardEvent(nsINode* aTarget,
+                                          const mozilla::WidgetKeyboardEvent& aEvent,
+                                          bool aEmbeddedCancelled) = 0;
+
+  /**
+   * Return whether or not the event is valid to be dispatched
+   */
+  virtual bool CanDispatchEvent(
+      const mozilla::WidgetGUIEvent* aEvent = nullptr) const = 0;
+
+  /**
+    * Gets the current target event frame from the PresShell
+    */
+  virtual nsIFrame* GetEventTargetFrame() = 0;
+
+  /**
+    * Gets the current target event frame from the PresShell
+    */
+  virtual already_AddRefed<nsIContent> GetEventTargetContent(
+                                                     mozilla::WidgetEvent* aEvent) = 0;
+
+  /**
+   * Get and set the history state for the current document
+   */
+
+  virtual nsresult CaptureHistoryState(nsILayoutHistoryState** aLayoutHistoryState) = 0;
+
+  /**
+   * Determine if reflow is currently locked
+   * returns true if reflow is locked, false otherwise
+   */
+  bool IsReflowLocked() const { return mIsReflowing; }
+
+  /**
+   * Called to find out if painting is suppressed for this presshell.  If it is suppressd,
+   * we don't allow the painting of any layer but the background, and we don't
+   * recur into our children.
+   */
+  bool IsPaintingSuppressed() const { return mPaintingSuppressed; }
+
+  /**
+   * Pause painting by freezing the refresh driver of this and all parent
+   * presentations. This may not have the desired effect if this pres shell
+   * has its own refresh driver.
+   */
+  virtual void PausePainting() = 0;
+
+  /**
+   * Resume painting by thawing the refresh driver of this and all parent
+   * presentations. This may not have the desired effect if this pres shell
+   * has its own refresh driver.
+   */
+  virtual void ResumePainting() = 0;
+
+  /**
+   * Unsuppress painting.
+   */
+  virtual void UnsuppressPainting() = 0;
+
+  /**
+   * Called to disable nsITheme support in a specific presshell.
+   */
+  void DisableThemeSupport()
+  {
+    // Doesn't have to be dynamic.  Just set the bool.
+    mIsThemeSupportDisabled = true;
+  }
+
+  /**
+   * Indicates whether theme support is enabled.
+   */
+  bool IsThemeSupportEnabled() const { return !mIsThemeSupportDisabled; }
+
+  /**
+   * Get the set of agent style sheets for this presentation
+   */
+  virtual nsresult GetAgentStyleSheets(
+      nsTArray<RefPtr<mozilla::StyleSheet>>& aSheets) = 0;
+
+  /**
+   * Replace the set of agent style sheets
+   */
+  virtual nsresult SetAgentStyleSheets(
+      const nsTArray<RefPtr<mozilla::StyleSheet>>& aSheets) = 0;
+
+  /**
+   * Add an override style sheet for this presentation
+   */
+  virtual nsresult AddOverrideStyleSheet(mozilla::StyleSheet* aSheet) = 0;
+
+  /**
+   * Remove an override style sheet
+   */
+  virtual nsresult RemoveOverrideStyleSheet(mozilla::StyleSheet* aSheet) = 0;
+
+  /**
+   * Reconstruct frames for all elements in the document
+   */
+  virtual nsresult ReconstructFrames() = 0;
+
+  /**
+   * Notify that a content node's state has changed
+   */
+  virtual void ContentStateChanged(nsIDocument* aDocument,
+                                   nsIContent* aContent,
+                                   mozilla::EventStates aStateMask) = 0;
+
+  /**
+   * See if reflow verification is enabled. To enable reflow verification add
+   * "verifyreflow:1" to your MOZ_LOG environment variable (any non-zero
+   * debug level will work). Or, call SetVerifyReflowEnable with true.
+   */
+  static bool GetVerifyReflowEnable();
+
+  /**
+   * Set the verify-reflow enable flag.
+   */
+  static void SetVerifyReflowEnable(bool aEnabled);
+
+  virtual nsIFrame* GetAbsoluteContainingBlock(nsIFrame* aFrame);
+
+#ifdef MOZ_REFLOW_PERF
+  virtual void DumpReflows() = 0;
+  virtual void CountReflows(const char * aName, nsIFrame * aFrame) = 0;
+  virtual void PaintCount(const char * aName,
+                                      nsRenderingContext* aRenderingContext,
+                                      nsPresContext * aPresContext,
+                                      nsIFrame * aFrame,
+                                      const nsPoint& aOffset,
+                                      uint32_t aColor) = 0;
+  virtual void SetPaintFrameCount(bool aOn) = 0;
+  virtual bool IsPaintingFrameCounts() = 0;
+#endif
+
+#ifdef DEBUG
+  // Debugging hooks
+  virtual void ListStyleContexts(nsIFrame *aRootFrame, FILE *out,
+                                 int32_t aIndent = 0) = 0;
+
+  virtual void ListStyleSheets(FILE *out, int32_t aIndent = 0) = 0;
+  virtual void VerifyStyleTree() = 0;
+#endif
+
+#ifdef ACCESSIBILITY
+  /**
+   * Return true if accessibility is active.
+   */
+  static bool IsAccessibilityActive();
+
+  /**
+   * Return accessibility service if accessibility is active.
+   */
+  static nsAccessibilityService* AccService();
+#endif
+
+  /**
+   * Stop all active elements (plugins and the caret) in this presentation and
+   * in the presentations of subdocuments.  Resets painting to a suppressed state.
+   * XXX this should include image animations
+   */
+  virtual void Freeze() = 0;
+  bool IsFrozen() { return mFrozen; }
+
+  /**
+   * Restarts active elements (plugins) in this presentation and in the
+   * presentations of subdocuments, then do a full invalidate of the content area.
+   */
+  virtual void Thaw() = 0;
+
+  virtual void FireOrClearDelayedEvents(bool aFireEvents) = 0;
+
+  /**
+   * When this shell is disconnected from its containing docshell, we
+   * lose our container pointer.  However, we'd still like to be able to target
+   * user events at the docshell's parent.  This pointer allows us to do that.
+   * It should not be used for any other purpose.
+   */
+  void SetForwardingContainer(const mozilla::WeakPtr<nsDocShell> &aContainer);
+
+  /**
+   * Render the document into an arbitrary gfxContext
+   * Designed for getting a picture of a document or a piece of a document
+   * Note that callers will generally want to call FlushPendingNotifications
+   * to get an up-to-date view of the document
+   * @param aRect is the region to capture into the offscreen buffer, in the
+   * root frame's coordinate system (if aIgnoreViewportScrolling is false)
+   * or in the root scrolled frame's coordinate system
+   * (if aIgnoreViewportScrolling is true). The coordinates are in appunits.
+   * @param aFlags see below;
+   *   set RENDER_IS_UNTRUSTED if the contents may be passed to malicious
+   * agents. E.g. we might choose not to paint the contents of sensitive widgets
+   * such as the file name in a file upload widget, and we might choose not
+   * to paint themes.
+   *   set RENDER_IGNORE_VIEWPORT_SCROLLING to ignore
+   * clipping and scrollbar painting due to scrolling in the viewport
+   *   set RENDER_CARET to draw the caret if one would be visible
+   * (by default the caret is never drawn)
+   *   set RENDER_USE_LAYER_MANAGER to force rendering to go through
+   * the layer manager for the window. This may be unexpectedly slow
+   * (if the layer manager must read back data from the GPU) or low-quality
+   * (if the layer manager reads back pixel data and scales it
+   * instead of rendering using the appropriate scaling). It may also
+   * slow everything down if the area rendered does not correspond to the
+   * normal visible area of the window.
+   *   set RENDER_ASYNC_DECODE_IMAGES to avoid having images synchronously
+   * decoded during rendering.
+   * (by default images decode synchronously with RenderDocument)
+   *   set RENDER_DOCUMENT_RELATIVE to render the document as if there has been
+   * no scrolling and interpret |aRect| relative to the document instead of the
+   * CSS viewport. Only considered if RENDER_IGNORE_VIEWPORT_SCROLLING is set
+   * or the document is in ignore viewport scrolling mode
+   * (nsIPresShell::SetIgnoreViewportScrolling/IgnoringViewportScrolling).
+   * @param aBackgroundColor a background color to render onto
+   * @param aRenderedContext the gfxContext to render to. We render so that
+   * one CSS pixel in the source document is rendered to one unit in the current
+   * transform.
+   */
+  enum {
+    RENDER_IS_UNTRUSTED = 0x01,
+    RENDER_IGNORE_VIEWPORT_SCROLLING = 0x02,
+    RENDER_CARET = 0x04,
+    RENDER_USE_WIDGET_LAYERS = 0x08,
+    RENDER_ASYNC_DECODE_IMAGES = 0x10,
+    RENDER_DOCUMENT_RELATIVE = 0x20,
+    RENDER_DRAWWINDOW_NOT_FLUSHING = 0x40
+  };
+  virtual nsresult RenderDocument(const nsRect& aRect, uint32_t aFlags,
+                                  nscolor aBackgroundColor,
+                                  gfxContext* aRenderedContext) = 0;
+
+  enum {
+    RENDER_IS_IMAGE = 0x100,
+    RENDER_AUTO_SCALE = 0x80
+  };
+
+  /**
+   * Renders a node aNode to a surface and returns it. The aRegion may be used
+   * to clip the rendering. This region is measured in CSS pixels from the
+   * edge of the presshell area. The aPoint, aScreenRect and aFlags arguments
+   * function in a similar manner as RenderSelection.
+   */
+  virtual already_AddRefed<mozilla::gfx::SourceSurface>
+  RenderNode(nsIDOMNode* aNode,
+             nsIntRegion* aRegion,
+             const mozilla::LayoutDeviceIntPoint aPoint,
+             mozilla::LayoutDeviceIntRect* aScreenRect,
+             uint32_t aFlags) = 0;
+
+  /**
+   * Renders a selection to a surface and returns it. This method is primarily
+   * intended to create the drag feedback when dragging a selection.
+   *
+   * aScreenRect will be filled in with the bounding rectangle of the
+   * selection area on screen.
+   *
+   * If the area of the selection is large and the RENDER_AUTO_SCALE flag is
+   * set, the image will be scaled down. The argument aPoint is used in this
+   * case as a reference point when determining the new screen rectangle after
+   * scaling. Typically, this will be the mouse position, so that the screen
+   * rectangle is positioned such that the mouse is over the same point in the
+   * scaled image as in the original. When scaling does not occur, the mouse
+   * point isn't used because the position can be determined from the displayed
+   * frames.
+   */
+  virtual already_AddRefed<mozilla::gfx::SourceSurface>
+  RenderSelection(nsISelection* aSelection,
+                  const mozilla::LayoutDeviceIntPoint aPoint,
+                  mozilla::LayoutDeviceIntRect* aScreenRect,
+                  uint32_t aFlags) = 0;
+
+  void AddWeakFrameInternal(nsWeakFrame* aWeakFrame);
+  virtual void AddWeakFrameExternal(nsWeakFrame* aWeakFrame);
+
+  void AddWeakFrame(nsWeakFrame* aWeakFrame)
+  {
+#ifdef MOZILLA_INTERNAL_API
+    AddWeakFrameInternal(aWeakFrame);
+#else
+    AddWeakFrameExternal(aWeakFrame);
+#endif
+  }
+
+  void RemoveWeakFrameInternal(nsWeakFrame* aWeakFrame);
+  virtual void RemoveWeakFrameExternal(nsWeakFrame* aWeakFrame);
+
+  void RemoveWeakFrame(nsWeakFrame* aWeakFrame)
+  {
+#ifdef MOZILLA_INTERNAL_API
+    RemoveWeakFrameInternal(aWeakFrame);
+#else
+    RemoveWeakFrameExternal(aWeakFrame);
+#endif
+  }
+
+#ifdef DEBUG
+  nsIFrame* GetDrawEventTargetFrame() { return mDrawEventTargetFrame; }
+#endif
+
+  /**
+   * Stop or restart non synthetic test mouse event handling on *all*
+   * presShells.
+   *
+   * @param aDisable If true, disable all non synthetic test mouse
+   * events on all presShells.  Otherwise, enable them.
+   */
+  virtual void DisableNonTestMouseEvents(bool aDisable) = 0;
+
+  /**
+   * Record the background color of the most recently drawn canvas. This color
+   * is composited on top of the user's default background color and then used
+   * to draw the background color of the canvas. See PresShell::Paint,
+   * PresShell::PaintDefaultBackground, and nsDocShell::SetupNewViewer;
+   * bug 488242, bug 476557 and other bugs mentioned there.
+   */
+  void SetCanvasBackground(nscolor aColor) { mCanvasBackgroundColor = aColor; }
+  nscolor GetCanvasBackground() { return mCanvasBackgroundColor; }
+
+  /**
+   * Use the current frame tree (if it exists) to update the background
+   * color of the most recently drawn canvas.
+   */
+  virtual void UpdateCanvasBackground() = 0;
+
+  /**
+   * Add a solid color item to the bottom of aList with frame aFrame and bounds
+   * aBounds. Checks first if this needs to be done by checking if aFrame is a
+   * canvas frame (if the FORCE_DRAW flag is passed then this check is skipped).
+   * aBackstopColor is composed behind the background color of the canvas, it is
+   * transparent by default.
+   */
+  enum {
+    FORCE_DRAW = 0x01
+  };
+  virtual void AddCanvasBackgroundColorItem(nsDisplayListBuilder& aBuilder,
+                                            nsDisplayList& aList,
+                                            nsIFrame* aFrame,
+                                            const nsRect& aBounds,
+                                            nscolor aBackstopColor = NS_RGBA(0,0,0,0),
+                                            uint32_t aFlags = 0) = 0;
+
+
+  /**
+   * Add a solid color item to the bottom of aList with frame aFrame and
+   * bounds aBounds representing the dark grey background behind the page of a
+   * print preview presentation.
+   */
+  virtual void AddPrintPreviewBackgroundItem(nsDisplayListBuilder& aBuilder,
+                                             nsDisplayList& aList,
+                                             nsIFrame* aFrame,
+                                             const nsRect& aBounds) = 0;
+
+  /**
+   * Computes the backstop color for the view: transparent if in a transparent
+   * widget, otherwise the PresContext default background color. This color is
+   * only visible if the contents of the view as a whole are translucent.
+   */
+  virtual nscolor ComputeBackstopColor(nsView* aDisplayRoot) = 0;
+
+  void ObserveNativeAnonMutationsForPrint(bool aObserve)
+  {
+    mObservesMutationsForPrint = aObserve;
+  }
+  bool ObservesNativeAnonMutationsForPrint()
+  {
+    return mObservesMutationsForPrint;
+  }
+
+  virtual nsresult SetIsActive(bool aIsActive) = 0;
+
+  bool IsActive()
+  {
+    return mIsActive;
+  }
+
+  // mouse capturing
+  static CapturingContentInfo gCaptureInfo;
+
+  class PointerCaptureInfo final
+  {
+  public:
+    nsCOMPtr<nsIContent> mPendingContent;
+    nsCOMPtr<nsIContent> mOverrideContent;
+
+    explicit PointerCaptureInfo(nsIContent* aPendingContent)
+      : mPendingContent(aPendingContent)
+    {
+      MOZ_COUNT_CTOR(PointerCaptureInfo);
+    }
+
+    ~PointerCaptureInfo()
+    {
+      MOZ_COUNT_DTOR(PointerCaptureInfo);
+    }
+
+    bool Empty()
+    {
+      return !(mPendingContent || mOverrideContent);
+    }
+  };
+
+  class PointerInfo final
+  {
+  public:
+    uint16_t mPointerType;
+    bool mActiveState;
+    bool mPrimaryState;
+    explicit PointerInfo(bool aActiveState, uint16_t aPointerType,
+                         bool aPrimaryState)
+      : mPointerType(aPointerType)
+      , mActiveState(aActiveState)
+      , mPrimaryState(aPrimaryState)
+    {
+    }
+  };
+
+  static void DispatchGotOrLostPointerCaptureEvent(bool aIsGotCapture,
+                                                   uint32_t aPointerId,
+                                                   uint16_t aPointerType,
+                                                   bool aIsPrimary,
+                                                   nsIContent* aCaptureTarget);
+  static PointerCaptureInfo* GetPointerCaptureInfo(uint32_t aPointerId);
+  static void SetPointerCapturingContent(uint32_t aPointerId,
+                                         nsIContent* aContent);
+  static void ReleasePointerCapturingContent(uint32_t aPointerId);
+  static nsIContent* GetPointerCapturingContent(uint32_t aPointerId);
+
+  // CheckPointerCaptureState checks cases, when got/lostpointercapture events
+  // should be fired.
+  static void CheckPointerCaptureState(uint32_t aPointerId,
+                                       uint16_t aPointerType, bool aIsPrimary);
+
+  // GetPointerInfo returns true if pointer with aPointerId is situated in
+  // device, false otherwise.
+  // aActiveState is additional information, which shows state of pointer like
+  // button state for mouse.
+  static bool GetPointerInfo(uint32_t aPointerId, bool& aActiveState);
+
+  // GetPointerType returns pointer type like mouse, pen or touch for pointer
+  // event with pointerId
+  static uint16_t GetPointerType(uint32_t aPointerId);
+
+  // GetPointerPrimaryState returns state of attribute isPrimary for pointer
+  // event with pointerId
+  static bool GetPointerPrimaryState(uint32_t aPointerId);
+
+  /**
+   * When capturing content is set, it traps all mouse events and retargets
+   * them at this content node. If capturing is not allowed
+   * (gCaptureInfo.mAllowed is false), then capturing is not set. However, if
+   * the CAPTURE_IGNOREALLOWED flag is set, the allowed state is ignored and
+   * capturing is set regardless. To disable capture, pass null for the value
+   * of aContent.
+   *
+   * If CAPTURE_RETARGETTOELEMENT is set, all mouse events are targeted at
+   * aContent only. Otherwise, mouse events are targeted at aContent or its
+   * descendants. That is, descendants of aContent receive mouse events as
+   * they normally would, but mouse events outside of aContent are retargeted
+   * to aContent.
+   *
+   * If CAPTURE_PREVENTDRAG is set then drags are prevented from starting while
+   * this capture is active.
+   *
+   * If CAPTURE_POINTERLOCK is set, similar to CAPTURE_RETARGETTOELEMENT, then
+   * events are targeted at aContent, but capturing is held more strongly (i.e.,
+   * calls to SetCapturingContent won't unlock unless CAPTURE_POINTERLOCK is
+   * set again).
+   */
+  static void SetCapturingContent(nsIContent* aContent, uint8_t aFlags);
+
+  /**
+   * Return the active content currently capturing the mouse if any.
+   */
+  static nsIContent* GetCapturingContent()
+  {
+    return gCaptureInfo.mContent;
+  }
+
+  /**
+   * Allow or disallow mouse capturing.
+   */
+  static void AllowMouseCapture(bool aAllowed)
+  {
+    gCaptureInfo.mAllowed = aAllowed;
+  }
+
+  /**
+   * Returns true if there is an active mouse capture that wants to prevent
+   * drags.
+   */
+  static bool IsMouseCapturePreventingDrag()
+  {
+    return gCaptureInfo.mPreventDrag && gCaptureInfo.mContent;
+  }
+
+  /**
+   * Keep track of how many times this presshell has been rendered to
+   * a window.
+   */
+  uint64_t GetPaintCount() { return mPaintCount; }
+  void IncrementPaintCount() { ++mPaintCount; }
+
+  /**
+   * Get the root DOM window of this presShell.
+   */
+  virtual already_AddRefed<nsPIDOMWindowOuter> GetRootWindow() = 0;
+
+  /**
+   * Get the layer manager for the widget of the root view, if it has
+   * one.
+   */
+  virtual LayerManager* GetLayerManager() = 0;
+
+  /**
+   * Return true iff there is a widget rendering this presShell and that
+   * widget is APZ-enabled.
+   */
+  virtual bool AsyncPanZoomEnabled() = 0;
+
+  /**
+   * Track whether we're ignoring viewport scrolling for the purposes
+   * of painting.  If we are ignoring, then layers aren't clipped to
+   * the CSS viewport and scrollbars aren't drawn.
+   */
+  virtual void SetIgnoreViewportScrolling(bool aIgnore) = 0;
+  bool IgnoringViewportScrolling() const
+  { return mRenderFlags & STATE_IGNORING_VIEWPORT_SCROLLING; }
+
+   /**
+   * Set a "resolution" for the document, which if not 1.0 will
+   * allocate more or fewer pixels for rescalable content by a factor
+   * of |resolution| in both dimensions.  Return NS_OK iff the
+   * resolution bounds are sane, and the resolution of this was
+   * actually updated.
+   *
+   * The resolution defaults to 1.0.
+   */
+  virtual nsresult SetResolution(float aResolution) = 0;
+  float GetResolution() const { return mResolution.valueOr(1.0); }
+  virtual float GetCumulativeResolution() = 0;
+
+  /**
+   * Calculate the cumulative scale resolution from this document up to
+   * but not including the root document.
+   */
+  virtual float GetCumulativeNonRootScaleResolution() = 0;
+
+  /**
+   * Was the current resolution set by the user or just default initialized?
+   */
+  bool IsResolutionSet() { return mResolution.isSome(); }
+
+  /**
+   * Similar to SetResolution() but also increases the scale of the content
+   * by the same amount.
+   */
+  virtual nsresult SetResolutionAndScaleTo(float aResolution) = 0;
+
+  /**
+   * Return whether we are scaling to the set resolution.
+   * This is initially false; it's set to true by a call to
+   * SetResolutionAndScaleTo(), and set to false by a call to SetResolution().
+   */
+  virtual bool ScaleToResolution() const = 0;
+
+  /**
+   * Used by session restore code to restore a resolution before the first
+   * paint.
+   */
+  virtual void SetRestoreResolution(float aResolution,
+                                    mozilla::LayoutDeviceIntSize aDisplaySize) = 0;
+
+  /**
+   * Returns whether we are in a DrawWindow() call that used the
+   * DRAWWINDOW_DO_NOT_FLUSH flag.
+   */
+  bool InDrawWindowNotFlushing() const
+  { return mRenderFlags & STATE_DRAWWINDOW_NOT_FLUSHING; }
+
+  /**
+   * Set the isFirstPaint flag.
+   */
+  void SetIsFirstPaint(bool aIsFirstPaint) { mIsFirstPaint = aIsFirstPaint; }
+
+  /**
+   * Get the isFirstPaint flag.
+   */
+  bool GetIsFirstPaint() const { return mIsFirstPaint; }
+
+  uint32_t GetPresShellId() { return mPresShellId; }
+
+  /**
+   * Dispatch a mouse move event based on the most recent mouse position if
+   * this PresShell is visible. This is used when the contents of the page
+   * moved (aFromScroll is false) or scrolled (aFromScroll is true).
+   */
+  virtual void SynthesizeMouseMove(bool aFromScroll) = 0;
+
+  enum PaintFlags {
+    /* Update the layer tree and paint PaintedLayers. If this is not specified,
+     * we may still have to do it if the layer tree lost PaintedLayer contents
+     * we need for compositing. */
+    PAINT_LAYERS = 0x01,
+    /* Composite layers to the window. */
+    PAINT_COMPOSITE = 0x02,
+    /* Sync-decode images. */
+    PAINT_SYNC_DECODE_IMAGES = 0x04
+  };
+  virtual void Paint(nsView* aViewToPaint, const nsRegion& aDirtyRegion,
+                     uint32_t aFlags) = 0;
+  virtual nsresult HandleEvent(nsIFrame* aFrame,
+                               mozilla::WidgetGUIEvent* aEvent,
+                               bool aDontRetargetEvents,
+                               nsEventStatus* aEventStatus,
+                               nsIContent** aTargetContent = nullptr) = 0;
+  virtual bool ShouldIgnoreInvalidation() = 0;
+  /**
+   * Notify that we're going to call Paint with PAINT_LAYERS
+   * on the pres shell for a widget (which might not be this one, since
+   * WillPaint is called on all presshells in the same toplevel window as the
+   * painted widget). This is issued at a time when it's safe to modify
+   * widget geometry.
+   */
+  virtual void WillPaint() = 0;
+  /**
+   * Notify that we're going to call Paint with PAINT_COMPOSITE.
+   * Fires on the presshell for the painted widget.
+   * This is issued at a time when it's safe to modify widget geometry.
+   */
+  virtual void WillPaintWindow() = 0;
+  /**
+   * Notify that we called Paint with PAINT_COMPOSITE.
+   * Fires on the presshell for the painted widget.
+   * This is issued at a time when it's safe to modify widget geometry.
+   */
+  virtual void DidPaintWindow() = 0;
+
+  /**
+   * Ensures that the refresh driver is running, and schedules a view
+   * manager flush on the next tick.
+   *
+   * @param aType PAINT_DELAYED_COMPRESS : Schedule a paint to be executed after a delay, and
+   * put FrameLayerBuilder in 'compressed' mode that avoids short cut optimizations.
+   */
+  enum PaintType {
+    PAINT_DEFAULT,
+    PAINT_DELAYED_COMPRESS
+  };
+  virtual void ScheduleViewManagerFlush(PaintType aType = PAINT_DEFAULT) = 0;
+  virtual void ClearMouseCaptureOnView(nsView* aView) = 0;
+  virtual bool IsVisible() = 0;
+  virtual void DispatchSynthMouseMove(mozilla::WidgetGUIEvent* aEvent,
+                                      bool aFlushOnHoverChange) = 0;
+
+  virtual void AddSizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf,
+                                      nsArenaMemoryStats *aArenaObjectsSize,
+                                      size_t *aPresShellSize,
+                                      size_t *aStyleSetsSize,
+                                      size_t *aTextRunsSize,
+                                      size_t *aPresContextSize) = 0;
+
+  /**
+   * Methods that retrieve the cached font inflation preferences.
+   */
+  uint32_t FontSizeInflationEmPerLine() const {
+    return mFontSizeInflationEmPerLine;
+  }
+
+  uint32_t FontSizeInflationMinTwips() const {
+    return mFontSizeInflationMinTwips;
+  }
+
+  uint32_t FontSizeInflationLineThreshold() const {
+    return mFontSizeInflationLineThreshold;
+  }
+
+  bool FontSizeInflationForceEnabled() const {
+    return mFontSizeInflationForceEnabled;
+  }
+
+  bool FontSizeInflationDisabledInMasterProcess() const {
+    return mFontSizeInflationDisabledInMasterProcess;
+  }
+
+  /**
+   * Determine if font size inflation is enabled. This value is cached until
+   * it becomes dirty.
+   *
+   * @returns true, if font size inflation is enabled; false otherwise.
+   */
+  bool FontSizeInflationEnabled();
+
+  /**
+   * Notify the pres shell that an event occurred making the current value of
+   * mFontSizeInflationEnabled invalid. This will schedule a recomputation of
+   * whether font size inflation is enabled on the next call to
+   * FontSizeInflationEnabled().
+   */
+  void NotifyFontSizeInflationEnabledIsDirty()
+  {
+    mFontSizeInflationEnabledIsDirty = true;
+  }
+
+  virtual void AddInvalidateHiddenPresShellObserver(nsRefreshDriver *aDriver) = 0;
+
+  void InvalidatePresShellIfHidden();
+  void CancelInvalidatePresShellIfHidden();
+
+
+  //////////////////////////////////////////////////////////////////////////////
+  // Approximate frame visibility tracking public API.
+  //////////////////////////////////////////////////////////////////////////////
+
+  /// Schedule an update of the list of approximately visible frames "soon".
+  /// This lets the refresh driver know that we want a visibility update in the
+  /// near future. The refresh driver applies its own heuristics and throttling
+  /// to decide when to actually perform the visibility update.
+  virtual void ScheduleApproximateFrameVisibilityUpdateSoon() = 0;
+
+  /// Schedule an update of the list of approximately visible frames "now". The
+  /// update runs asynchronously, but it will be posted to the event loop
+  /// immediately. Prefer the "soon" variation of this method when possible, as
+  /// this variation ignores the refresh driver's heuristics.
+  virtual void ScheduleApproximateFrameVisibilityUpdateNow() = 0;
+
+  /// Clears the current list of approximately visible frames on this pres shell
+  /// and replaces it with frames that are in the display list @aList.
+  virtual void RebuildApproximateFrameVisibilityDisplayList(const nsDisplayList& aList) = 0;
+  virtual void RebuildApproximateFrameVisibility(nsRect* aRect = nullptr,
+                                                 bool aRemoveOnly = false) = 0;
+
+  /// Ensures @aFrame is in the list of approximately visible frames.
+  virtual void EnsureFrameInApproximatelyVisibleList(nsIFrame* aFrame) = 0;
+
+  /// Removes @aFrame from the list of approximately visible frames if present.
+  virtual void RemoveFrameFromApproximatelyVisibleList(nsIFrame* aFrame) = 0;
+
+  /// Whether we should assume all frames are visible.
+  virtual bool AssumeAllFramesVisible() = 0;
+
+
+  /**
+   * Returns whether the document's style set's rule processor for the
+   * specified level of the cascade is shared by multiple style sets.
+   *
+   * @param aSheetType One of the nsIStyleSheetService.*_SHEET constants.
+   */
+  nsresult HasRuleProcessorUsedByMultipleStyleSets(uint32_t aSheetType,
+                                                   bool* aRetVal);
+
+  /**
+   * Refresh observer management.
+   */
+protected:
+  virtual bool AddRefreshObserverExternal(nsARefreshObserver* aObserver,
+                                          mozFlushType aFlushType);
+  bool AddRefreshObserverInternal(nsARefreshObserver* aObserver,
+                                  mozFlushType aFlushType);
+  virtual bool RemoveRefreshObserverExternal(nsARefreshObserver* aObserver,
+                                             mozFlushType aFlushType);
+  bool RemoveRefreshObserverInternal(nsARefreshObserver* aObserver,
+                                     mozFlushType aFlushType);
+
+  /**
+   * Do computations necessary to determine if font size inflation is enabled.
+   * This value is cached after computation, as the computation is somewhat
+   * expensive.
+   */
+  void RecomputeFontSizeInflationEnabled();
+
+  void RecordAlloc(void* aPtr) {
+#ifdef DEBUG
+    MOZ_ASSERT(!mAllocatedPointers.Contains(aPtr));
+    mAllocatedPointers.PutEntry(aPtr);
+#endif
+  }
+
+  void RecordFree(void* aPtr) {
+#ifdef DEBUG
+    MOZ_ASSERT(mAllocatedPointers.Contains(aPtr));
+    mAllocatedPointers.RemoveEntry(aPtr);
+#endif
+  }
+
+public:
+  bool AddRefreshObserver(nsARefreshObserver* aObserver,
+                          mozFlushType aFlushType) {
+#ifdef MOZILLA_INTERNAL_API
+    return AddRefreshObserverInternal(aObserver, aFlushType);
+#else
+    return AddRefreshObserverExternal(aObserver, aFlushType);
+#endif
+  }
+
+  bool RemoveRefreshObserver(nsARefreshObserver* aObserver,
+                             mozFlushType aFlushType) {
+#ifdef MOZILLA_INTERNAL_API
+    return RemoveRefreshObserverInternal(aObserver, aFlushType);
+#else
+    return RemoveRefreshObserverExternal(aObserver, aFlushType);
+#endif
+  }
+
+  virtual bool AddPostRefreshObserver(nsAPostRefreshObserver* aObserver);
+  virtual bool RemovePostRefreshObserver(nsAPostRefreshObserver* aObserver);
+
+  /**
+   * Initialize and shut down static variables.
+   */
+  static void InitializeStatics();
+  static void ReleaseStatics();
+
+  // If a frame in the subtree rooted at aFrame is capturing the mouse then
+  // clears that capture.
+  static void ClearMouseCapture(nsIFrame* aFrame);
+
+  void SetScrollPositionClampingScrollPortSize(nscoord aWidth, nscoord aHeight);
+  bool IsScrollPositionClampingScrollPortSizeSet() {
+    return mScrollPositionClampingScrollPortSizeSet;
+  }
+  nsSize GetScrollPositionClampingScrollPortSize() {
+    NS_ASSERTION(mScrollPositionClampingScrollPortSizeSet, "asking for scroll port when its not set?");
+    return mScrollPositionClampingScrollPortSize;
+  }
+
+  virtual void WindowSizeMoveDone() = 0;
+  virtual void SysColorChanged() = 0;
+  virtual void ThemeChanged() = 0;
+  virtual void BackingScaleFactorChanged() = 0;
+
+  /**
+   * Documents belonging to an invisible DocShell must not be painted ever.
+   */
+  bool IsNeverPainting() {
+    return mIsNeverPainting;
+  }
+
+  void SetNeverPainting(bool aNeverPainting) {
+    mIsNeverPainting = aNeverPainting;
+  }
+
+  bool HasPendingReflow() const
+    { return mReflowScheduled || mReflowContinueTimer; }
+
+  void SyncWindowProperties(nsView* aView);
+
+#ifdef ANDROID
+  virtual nsIDocument* GetTouchEventTargetDocument() = 0;
+#endif
+
+protected:
+  friend class nsRefreshDriver;
+
+  // IMPORTANT: The ownership implicit in the following member variables
+  // has been explicitly checked.  If you add any members to this class,
+  // please make the ownership explicit (pinkerton, scc).
+
+  // These are the same Document and PresContext owned by the DocViewer.
+  // we must share ownership.
+  nsCOMPtr<nsIDocument>     mDocument;
+  RefPtr<nsPresContext>   mPresContext;
+  mozilla::StyleSetHandle   mStyleSet;      // [OWNS]
+  nsCSSFrameConstructor*    mFrameConstructor; // [OWNS]
+  nsViewManager*           mViewManager;   // [WEAK] docViewer owns it so I don't have to
+  nsPresArena               mFrameArena;
+  RefPtr<nsFrameSelection> mSelection;
+  // Pointer into mFrameConstructor - this is purely so that FrameManager() and
+  // GetRootFrame() can be inlined:
+  nsFrameManagerBase*       mFrameManager;
+  mozilla::WeakPtr<nsDocShell>                 mForwardingContainer;
+  nsRefreshDriver* MOZ_UNSAFE_REF("These two objects hold weak references "
+                                  "to each other, and the validity of this "
+                                  "member is ensured by the logic in nsIPresShell.")
+                            mHiddenInvalidationObserverRefreshDriver;
+#ifdef ACCESSIBILITY
+  mozilla::a11y::DocAccessible* mDocAccessible;
+#endif
+
+  // At least on Win32 and Mac after interupting a reflow we need to post
+  // the resume reflow event off a timer to avoid event starvation because
+  // posted messages are processed before other messages when the modal
+  // moving/sizing loop is running, see bug 491700 for details.
+  nsCOMPtr<nsITimer>        mReflowContinueTimer;
+
+#ifdef MOZ_B2G
+  // Forward hardware key events to the input-method-app
+  nsCOMPtr<nsIHardwareKeyHandler> mHardwareKeyHandler;
+#endif // MOZ_B2G
+
+#ifdef DEBUG
+  nsIFrame*                 mDrawEventTargetFrame;
+
+  // We track allocated pointers in a debug-only hashtable to assert against
+  // missing/double frees.
+  nsTHashtable<nsPtrHashKey<void>> mAllocatedPointers;
+#endif
+
+
+  // Count of the number of times this presshell has been painted to a window.
+  uint64_t                  mPaintCount;
+
+  nsSize                    mScrollPositionClampingScrollPortSize;
+
+  // A list of weak frames. This is a pointer to the last item in the list.
+  nsWeakFrame*              mWeakFrames;
+
+  // Most recent canvas background color.
+  nscolor                   mCanvasBackgroundColor;
+
+  // Used to force allocation and rendering of proportionally more or
+  // less pixels in both dimensions.
+  mozilla::Maybe<float>     mResolution;
+
+  int16_t                   mSelectionFlags;
+
+  // Flags controlling how our document is rendered.  These persist
+  // between paints and so are tied with retained layer pixels.
+  // PresShell flushes retained layers when the rendering state
+  // changes in a way that prevents us from being able to (usefully)
+  // re-use old pixels.
+  RenderFlags               mRenderFlags;
+
+  // Indicates that the whole document must be restyled.  Changes to scoped
+  // style sheets are recorded in mChangedScopeStyleRoots rather than here
+  // in mStylesHaveChanged.
+  bool                      mStylesHaveChanged : 1;
+  bool                      mDidInitialize : 1;
+  bool                      mIsDestroying : 1;
+  bool                      mIsZombie : 1;
+  bool                      mIsReflowing : 1;
+
+  // For all documents we initially lock down painting.
+  bool                      mPaintingSuppressed : 1;
+
+  // Whether or not form controls should use nsITheme in this shell.
+  bool                      mIsThemeSupportDisabled : 1;
+
+  bool                      mIsActive : 1;
+  bool                      mFrozen : 1;
+  bool                      mIsFirstPaint : 1;
+  bool                      mObservesMutationsForPrint : 1;
+
+  // If true, we have a reflow scheduled. Guaranteed to be false if
+  // mReflowContinueTimer is non-null.
+  bool                      mReflowScheduled : 1;
+
+  bool                      mSuppressInterruptibleReflows : 1;
+  bool                      mScrollPositionClampingScrollPortSizeSet : 1;
+
+  uint32_t                  mPresShellId;
+
+  // List of subtrees rooted at style scope roots that need to be restyled.
+  // When a change to a scoped style sheet is made, we add the style scope
+  // root to this array rather than setting mStylesHaveChanged = true, since
+  // we know we don't need to restyle the whole document.  However, if in the
+  // same update block we have already had other changes that require
+  // the whole document to be restyled (i.e., mStylesHaveChanged is already
+  // true), then we don't bother adding the scope root here.
+  AutoTArray<RefPtr<mozilla::dom::Element>,1> mChangedScopeStyleRoots;
+
+  static nsIContent*        gKeyDownTarget;
+
+  // Cached font inflation values. This is done to prevent changing of font
+  // inflation until a page is reloaded.
+  uint32_t mFontSizeInflationEmPerLine;
+  uint32_t mFontSizeInflationMinTwips;
+  uint32_t mFontSizeInflationLineThreshold;
+  bool mFontSizeInflationForceEnabled;
+  bool mFontSizeInflationDisabledInMasterProcess;
+  bool mFontSizeInflationEnabled;
+  bool mPaintingIsFrozen;
+
+  // Dirty bit indicating that mFontSizeInflationEnabled needs to be recomputed.
+  bool mFontSizeInflationEnabledIsDirty;
+
+  // If a document belongs to an invisible DocShell, this flag must be set
+  // to true, so we can avoid any paint calls for widget related to this
+  // presshell.
+  bool mIsNeverPainting;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(nsIPresShell, NS_IPRESSHELL_IID)
+
+#endif /* nsIPresShell_h___ */