Use recomputed interest rect only if it changed enough

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

 /*
  * Copyright (C) 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 136 matching lines @@
     void finishAccumulatingSquashingLayers(size_t nextSquashedLayerIndex);
     void updateRenderingContext();
     void updateShouldFlattenTransform();
 
     // GraphicsLayerClient interface
     void notifyAnimationStarted(const GraphicsLayer*, double monotonicTime, int group) override;
     void notifyFirstPaint() override;
     void notifyFirstTextPaint() override;
     void notifyFirstImagePaint() override;
 
-    void paintContents(const GraphicsLayer*, GraphicsContext&, GraphicsLayerPaintingPhase, const IntRect* clip) const override;
+    IntRect paintContents(const GraphicsLayer*, GraphicsContext&, GraphicsLayerPaintingPhase, const IntRect* interestRect) const override;
     bool isTrackingPaintInvalidations() const override;
 
 #if ENABLE(ASSERT)
     void verifyNotPainting() override;
 #endif
 
     LayoutRect contentsBox() const;
 
     GraphicsLayer* layerForHorizontalScrollbar() const { return m_layerForHorizontalScrollbar.get(); }
     GraphicsLayer* layerForVerticalScrollbar() const { return m_layerForVerticalScrollbar.get(); }
@@ skipping 266 matching lines @@
 
     LayoutSize m_contentOffsetInCompositingLayer;
     unsigned m_contentOffsetInCompositingLayerDirty : 1;
 
     unsigned m_pendingUpdateScope : 2;
     unsigned m_isMainFrameLayoutViewLayer : 1;
 
     unsigned m_backgroundLayerPaintsFixedRootBackground : 1;
     unsigned m_scrollingContentsAreEmpty : 1;
 
-    mutable IntRect m_previousPaintInterestRect;
-
     friend class CompositedLayerMappingTest;
 };
 
 } // namespace blink
 
 #endif // CompositedLayerMapping_h