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

third_party/WebKit/public/platform/WebContentLayerClient.h

Index: third_party/WebKit/public/platform/WebContentLayerClient.h
diff --git a/third_party/WebKit/public/platform/WebContentLayerClient.h b/third_party/WebKit/public/platform/WebContentLayerClient.h
index 7e28aeeec6436c7b7b08faaa1ca92d776f8c6b3f..f0f53e0a4fb0ba20fbd3c12e17c8db567bc3c7e0 100644
--- a/third_party/WebKit/public/platform/WebContentLayerClient.h
+++ b/third_party/WebKit/public/platform/WebContentLayerClient.h
@@ -28,10 +28,14 @@
 
 #include "WebCommon.h"
 
+namespace gfx {
+class Rect;
+}
+
 namespace blink {
 
-class WebDisplayItemList;
 struct WebRect;
+class WebDisplayItemList;
 
 class BLINK_PLATFORM_EXPORT WebContentLayerClient {
 public:
@@ -42,6 +46,8 @@ public:
         DisplayListPaintingDisabled
     };
 
+    virtual gfx::Rect paintableRegion() = 0;
+
     // Paints the content area for the layer, typically dirty rects submitted
     // through WebContentLayer::setNeedsDisplayInRect, submitting drawing commands
     // to populate the WebDisplayItemList.