Use recomputed interest rect only if it changed enough

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h

Index: third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h
index a479f84d702141b8b1ad5fb665a8a9b1b075054c..758b9ca083f19879ebfb8be5b7289456e294f6ed 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h
@@ -154,7 +154,10 @@ public:
     void notifyFirstTextPaint() override;
     void notifyFirstImagePaint() override;
 
-    void paintContents(const GraphicsLayer*, GraphicsContext&, GraphicsLayerPaintingPhase, const IntRect* clip) const override;
+    IntRect computeInterestRect(const GraphicsLayer*, const IntRect& previousInterestRect) const override;
+    bool needsRepaint() const override;
+    void paintContents(const GraphicsLayer*, GraphicsContext&, GraphicsLayerPaintingPhase, const IntRect& interestRect) const override;
+
     bool isTrackingPaintInvalidations() const override;
 
 #if ENABLE(ASSERT)
@@ -194,7 +197,7 @@ public:
     void assertNeedsToUpdateGraphicsLayerBitsCleared() {  ASSERT(m_pendingUpdateScope == GraphicsLayerUpdateNone); }
 #endif
 
-    String debugName(const GraphicsLayer*) override;
+    String debugName(const GraphicsLayer*) const override;
 
     LayoutSize contentOffsetInCompositingLayer() const;
 
@@ -212,7 +215,7 @@ public:
     String debugName() const { return "CompositedLayerMapping for " + owningLayer().debugName(); }
 
 private:
-    static IntRect computeInterestRect(const GraphicsLayer*, LayoutObject* owningLayoutObject);
+    static IntRect recomputeInterestRect(const GraphicsLayer*, LayoutObject* owningLayoutObject);
     static bool interestRectChangedEnoughToRepaint(const IntRect& previousInterestRect, const IntRect& newInterestRect, const IntSize& layerSize);
 
     static const GraphicsLayerPaintInfo* containingSquashedLayer(const LayoutObject*,  const Vector<GraphicsLayerPaintInfo>& layers, unsigned maxSquashedLayerIndex);
@@ -316,8 +319,6 @@ private:
     // not appear earlier in the set of layers for this object.
     bool invalidateLayerIfNoPrecedingEntry(size_t);
 
-    void paintContentsInternal(const GraphicsLayer*, GraphicsContext&, GraphicsLayerPaintingPhase, const IntRect& interestRect) const;
-
     PaintLayer& m_owningLayer;
 
     // The hierarchy of layers that is maintained by the CompositedLayerMapping looks like this:
@@ -441,8 +442,6 @@ private:
     unsigned m_backgroundLayerPaintsFixedRootBackground : 1;
     unsigned m_scrollingContentsAreEmpty : 1;
 
-    mutable IntRect m_previousPaintInterestRect;
-
     friend class CompositedLayerMappingTest;
 };