Never call GraphicsLayer::paint when fetching painted output from cc.

third_party/WebKit/public/platform/WebContentLayerClient.h

 /*
  * Copyright (C) 2011 Google 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
@@ skipping 22 matching lines @@
 }
 
 namespace blink {
 
 struct WebRect;
 class WebDisplayItemList;
 
 class BLINK_PLATFORM_EXPORT WebContentLayerClient {
 public:
     enum PaintingControlSetting {
+        // Returns the last PaintArtifact produced.
         PaintDefaultBehavior,
+        // Paints the content to simulate the behavior of FrameView::synchronizedPaint.
+        PaintDefaultBehaviorForTest,
         DisplayListConstructionDisabled,
         DisplayListCachingDisabled,
         DisplayListPaintingDisabled,
         SubsequenceCachingDisabled
     };
 
     // The paintable region is the rectangular region, within the bounds of the layer
     // this client paints, that the client is capable of painting via paintContents().
     // Calling paintContents will return a WebDisplayitemList that is guaranteed valid
     // only within this region.
@@ skipping 15 matching lines @@
     // result includes data cached internally during painting.
     virtual size_t approximateUnsharedMemoryUsage() const { return 0; }
 
 protected:
     virtual ~WebContentLayerClient() { }
 };
 
 } // namespace blink
 
 #endif // WebContentLayerClient_h