Use recomputed interest rect only if it changed enough

third_party/WebKit/Source/platform/graphics/GraphicsLayer.h

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. 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
@@ skipping 228 matching lines @@
 
     void setScrollableArea(ScrollableArea*, bool isViewport);
     ScrollableArea* scrollableArea() const { return m_scrollableArea; }
 
     WebContentLayer* contentLayer() const { return m_layer.get(); }
 
     static void registerContentsLayer(WebLayer*);
     static void unregisterContentsLayer(WebLayer*);
 
     // GraphicsContextPainter implementation.
-    void paint(GraphicsContext&, const IntRect* clip) override;
+    void paint(GraphicsContext&, const IntRect* interestRect) override;
 
     // WebCompositorAnimationDelegate implementation.
     void notifyAnimationStarted(double monotonicTime, int group) override;
     void notifyAnimationFinished(double monotonicTime, int group) override;
 
     // WebLayerScrollClient implementation.
     void didScroll() override;
 
     PaintController* paintController() override;
 
     // Exposed for tests.
     WebLayer* contentsLayer() const { return m_contentsLayer; }
 
     static void setDrawDebugRedFillForTesting(bool);
     ContentLayerDelegate* contentLayerDelegateForTesting() const { return m_contentLayerDelegate.get(); }
 
 #ifndef NDEBUG
     DisplayItemClient displayItemClient() const { return toDisplayItemClient(this); }
     String debugName() const { return m_client->debugName(this) + " debug red fill"; }
 #endif
 
+    IntRect previousInterestRect() const { return m_previousInterestRect; }
+
 protected:
     String debugName(WebLayer*) const;
 
     explicit GraphicsLayer(GraphicsLayerClient*);
     // GraphicsLayerFactoryChromium that wants to create a GraphicsLayer need to be friends.
     friend class GraphicsLayerFactoryChromium;
     // for testing
     friend class FakeGraphicsLayerFactory;
 
 private:
@@ skipping 86 matching lines @@
     Vector<LinkHighlight*> m_linkHighlights;
 
     OwnPtr<ContentLayerDelegate> m_contentLayerDelegate;
 
     GC_PLUGIN_IGNORE("509911")
     ScrollableArea* m_scrollableArea;
     GraphicsLayerDebugInfo m_debugInfo;
     int m_3dRenderingContext;
 
     OwnPtr<PaintController> m_paintController;
+
+    IntRect m_previousInterestRect;
 };
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the blink namespace for ease of invocation from gdb.
 void PLATFORM_EXPORT showGraphicsLayerTree(const blink::GraphicsLayer*);
 #endif
 
 #endif // GraphicsLayer_h