Backout 3ad33d09825a (bug 1059014 part 3) because the removed code is less dead than it first appears.

docshell/base/nsIContentViewer.idl

@@ -31,7 +31,7 @@ class nsDOMNavigationTiming;
 [ptr] native nsDOMNavigationTimingPtr(nsDOMNavigationTiming);
 [ref] native nsIContentViewerTArray(nsTArray<nsCOMPtr<nsIContentViewer> >);
 
-[scriptable, builtinclass, uuid(91b6c1f3-fc5f-43a9-88f4-9286bd19387f)]
+[scriptable, builtinclass, uuid(2da17016-7851-4a45-a7a8-00b360e01595)]
 interface nsIContentViewer : nsISupports
 {
   [noscript] void init(in nsIWidgetPtr aParentWidget,
@@ -229,6 +229,18 @@ interface nsIContentViewer : nsISupports
    */
   [noscript] void appendSubtree(in nsIContentViewerTArray array);
 
+  /**
+   * Instruct the refresh driver to discontinue painting until further
+   * notice.
+   */
+  void pausePainting();
+
+  /**
+   * Instruct the refresh driver to resume painting after a previous call to
+   * pausePainting().
+   */
+  void resumePainting();
+
   /*
    * Render the document as if being viewed on a device with the specified
    * media type. This will cause a reflow.

layout/base/nsDocumentViewer.cpp

@@ -2774,6 +2774,17 @@ nsDocumentViewer::CallChildren(CallChildFunc aFunc, void* aClosure)
   }
 }
 
+static void
+ChangeChildPaintingEnabled(nsIContentViewer* aChild, void* aClosure)
+{
+  bool* enablePainting = (bool*) aClosure;
+  if (*enablePainting) {
+    aChild->ResumePainting();
+  } else {
+    aChild->PausePainting();
+  }
+}
+
 struct ZoomInfo
 {
   float mZoom;
@@ -3203,6 +3214,34 @@ NS_IMETHODIMP nsDocumentViewer::AppendSubtree(nsTArray<nsCOMPtr<nsIContentViewer
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsDocumentViewer::PausePainting()
+{
+  bool enablePaint = false;
+  CallChildren(ChangeChildPaintingEnabled, &enablePaint);
+
+  nsIPresShell* presShell = GetPresShell();
+  if (presShell) {
+    presShell->PausePainting();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocumentViewer::ResumePainting()
+{
+  bool enablePaint = true;
+  CallChildren(ChangeChildPaintingEnabled, &enablePaint);
+
+  nsIPresShell* presShell = GetPresShell();
+  if (presShell) {
+    presShell->ResumePainting();
+  }
+
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsDocumentViewer::GetContentSize(int32_t* aWidth, int32_t* aHeight)
 {

layout/base/nsIPresShell.h

@@ -140,10 +140,10 @@ typedef struct CapturingContentInfo {
   mozilla::StaticRefPtr<nsIContent> mContent;
 } CapturingContentInfo;
 
-// 327d78a0-0680-4709-b209-1cf9578720e6
+// e3042b8d-0cc0-4ee6-baca-fec1ba89ee97
 #define NS_IPRESSHELL_IID \
-{ 0x327d78a0, 0x0680, 0x4709, \
-  { 0xb2, 0x09, 0x1c, 0xf9, 0x57, 0x87, 0x20, 0xe6 } }
+{ 0xe3042b8d, 0x0cc0, 0x4ee6, \
+  { 0xba, 0xca, 0xfe, 0xc1, 0xba, 0x89, 0xee, 0x97 } }
 
 // debug VerifyReflow flags
 #define VERIFY_REFLOW_ON                    0x01
@@ -936,6 +936,20 @@ public:
    */
   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.
    */
@@ -1799,6 +1813,7 @@ protected:
   bool mFontSizeInflationForceEnabled;
   bool mFontSizeInflationDisabledInMasterProcess;
   bool mFontSizeInflationEnabled;
+  bool mPaintingIsFrozen;
 
   // Dirty bit indicating that mFontSizeInflationEnabled needs to be recomputed.
   bool mFontSizeInflationEnabledIsDirty;

layout/base/nsPresShell.cpp

@@ -799,6 +799,7 @@ PresShell::PresShell()
     addedPointerEventEnabled = true;
   }
 
+  mPaintingIsFrozen = false;
   mHasCSSBackgroundColor = true;
   mIsLastChromeOnlyEscapeKeyConsumed = false;
   mHasReceivedPaintMessage = false;
@@ -822,6 +823,13 @@ PresShell::~PresShell()
                mLastCallbackEventRequest == nullptr,
                "post-reflow queues not empty.  This means we're leaking");
 
+  // Verify that if painting was frozen, but we're being removed from the tree,
+  // that we now re-enable painting on our refresh driver, since it may need to
+  // be re-used by another presentation.
+  if (mPaintingIsFrozen) {
+    mPresContext->RefreshDriver()->Thaw();
+  }
+
 #ifdef DEBUG
   MOZ_ASSERT(mPresArenaAllocCount == 0,
              "Some pres arena objects were not freed");
@@ -10843,6 +10851,26 @@ nsIPresShell::FontSizeInflationEnabled()
   return mFontSizeInflationEnabled;
 }
 
+void
+PresShell::PausePainting()
+{
+  if (GetPresContext()->RefreshDriver()->PresContext() != GetPresContext())
+    return;
+
+  mPaintingIsFrozen = true;
+  GetPresContext()->RefreshDriver()->Freeze();
+}
+
+void
+PresShell::ResumePainting()
+{
+  if (GetPresContext()->RefreshDriver()->PresContext() != GetPresContext())
+    return;
+
+  mPaintingIsFrozen = false;
+  GetPresContext()->RefreshDriver()->Thaw();
+}
+
 void
 nsIPresShell::SyncWindowProperties(nsView* aView)
 {

layout/base/nsPresShell.h

@@ -738,6 +738,9 @@ protected:
   virtual void ThemeChanged() override { mPresContext->ThemeChanged(); }
   virtual void BackingScaleFactorChanged() override { mPresContext->UIResolutionChanged(); }
 
+  virtual void PausePainting() override;
+  virtual void ResumePainting() override;
+
   void UpdateImageVisibility();
   void UpdateActivePointerState(mozilla::WidgetGUIEvent* aEvent);