Use recomputed interest rect only if it changed enough

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

Index: third_party/WebKit/Source/platform/graphics/GraphicsLayerClient.h
diff --git a/third_party/WebKit/Source/platform/graphics/GraphicsLayerClient.h b/third_party/WebKit/Source/platform/graphics/GraphicsLayerClient.h
index e2406d5957e6f644cdf8891477fe1079cf4bcae8..a696b129efd11d724fc8004c78a153b54fb30ff5 100644
--- a/third_party/WebKit/Source/platform/graphics/GraphicsLayerClient.h
+++ b/third_party/WebKit/Source/platform/graphics/GraphicsLayerClient.h
@@ -69,7 +69,9 @@ public:
     virtual void notifyFirstTextPaint() { }
     virtual void notifyFirstImagePaint() { }
 
-    virtual void paintContents(const GraphicsLayer*, GraphicsContext&, GraphicsLayerPaintingPhase, const IntRect* inClip) const = 0;
+    // Paints contents covering interest rect if given, or covering the default interest rect calculated based
+    // on the layer size and the visible area. Returns the actual interest rect used.
+    virtual IntRect paintContents(const GraphicsLayer*, GraphicsContext&, GraphicsLayerPaintingPhase, const IntRect* interestRect) const = 0;
     virtual bool isTrackingPaintInvalidations() const { return false; }
 
     virtual String debugName(const GraphicsLayer*) = 0;