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

cc/blink/web_content_layer_impl.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_BLINK_WEB_CONTENT_LAYER_IMPL_H_
 #define CC_BLINK_WEB_CONTENT_LAYER_IMPL_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "cc/blink/cc_blink_export.h"
 #include "cc/blink/web_layer_impl.h"
@@ skipping 16 matching lines @@
  public:
   CC_BLINK_EXPORT explicit WebContentLayerImpl(blink::WebContentLayerClient*);
 
   // WebContentLayer implementation.
   blink::WebLayer* layer() override;
 
  protected:
   ~WebContentLayerImpl() override;
 
   // ContentLayerClient implementation.
+  gfx::Rect PaintableRegion() override;
   scoped_refptr<cc::DisplayItemList> PaintContentsToDisplayList(
       const gfx::Rect& clip,
       PaintingControlSetting painting_control) override;
   bool FillsBoundsCompletely() const override;
   size_t GetApproximateUnsharedMemoryUsage() const override;
 
   scoped_ptr<WebLayerImpl> layer_;
   blink::WebContentLayerClient* client_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(WebContentLayerImpl);
 };
 
 }  // namespace cc_blink
 
 #endif  // CC_BLINK_WEB_CONTENT_LAYER_IMPL_H_