Turn off computation of the interest rect in cc in synchronized paint mode.

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

 /*
  * Copyright (C) 2009 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 274 matching lines @@
     if (offset == m_offsetFromLayoutObject)
         return;
 
     m_offsetFromLayoutObject = offset;
 
     // If the compositing layer offset changes, we need to repaint.
     if (shouldSetNeedsDisplay == SetNeedsDisplay)
         setNeedsDisplay();
 }
 
+IntRect GraphicsLayer::interestRect()
+{
+    return m_previousInterestRect;
+}
+
 void GraphicsLayer::paint(GraphicsContext& context, const IntRect* interestRect)
 {
     ASSERT(interestRect || RuntimeEnabledFeatures::slimmingPaintSynchronizedPaintingEnabled());
     ASSERT(drawsContent());
 
     if (!m_client)
         return;
     if (firstPaintInvalidationTrackingEnabled())
         m_debugInfo.clearAnnotatedInvalidateRects();
     incrementPaintCount();
@@ skipping 900 matching lines @@
 {
     if (!layer) {
         fprintf(stderr, "Cannot showGraphicsLayerTree for (nil).\n");
         return;
     }
 
     String output = layer->layerTreeAsText(blink::LayerTreeIncludesDebugInfo);
     fprintf(stderr, "%s\n", output.utf8().data());
 }
 #endif