Use recomputed interest rect only if it changed enough

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

Index: third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
diff --git a/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h b/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
index 48105ffcf855fe35153749a9584b24b3ea9b1818..1d3b64ecb253bd3ed7d37c99b5ba040c7020ce47 100644
--- a/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
+++ b/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
@@ -246,7 +246,7 @@ public:
     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;
@@ -268,6 +268,8 @@ public:
     String debugName() const { return m_client->debugName(this) + " debug red fill"; }
 #endif
 
+    IntRect previousInterestRect() const { return m_previousInterestRect; }
+
 protected:
     String debugName(WebLayer*) const;
 
@@ -374,6 +376,8 @@ private:
     int m_3dRenderingContext;
 
     OwnPtr<PaintController> m_paintController;
+
+    IntRect m_previousInterestRect;
 };
 
 } // namespace blink