Make composited scrolling codepaths co-operate.

Source/web/tests/ScrollingCoordinatorChromiumTest.cpp

 /*
  * Copyright (C) 2012 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
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 236 matching lines @@
 }
 
 TEST_F(ScrollingCoordinatorChromiumTest, nonFastScrollableRegion)
 {
     registerMockedHttpURLLoad("non-fast-scrollable.html");
     navigateTo(m_baseURL + "non-fast-scrollable.html");
 
     WebLayer* rootScrollLayer = getRootScrollLayer();
     WebVector<WebRect> nonFastScrollableRegion = rootScrollLayer->nonFastScrollableRegion();
 
-    ASSERT_EQ(1u, nonFastScrollableRegion.size());
-    ASSERT_EQ(WebRect(8, 8, 10, 10), nonFastScrollableRegion[0]);
+    ASSERT_EQ(0u, nonFastScrollableRegion.size());
 }
 
 TEST_F(ScrollingCoordinatorChromiumTest, wheelEventHandler)
 {
     registerMockedHttpURLLoad("wheel-event-handler.html");
     navigateTo(m_baseURL + "wheel-event-handler.html");
 
     WebLayer* rootScrollLayer = getRootScrollLayer();
     ASSERT_TRUE(rootScrollLayer->haveWheelEventHandlers());
 }
@@ skipping 128 matching lines @@
 
 TEST_F(ScrollingCoordinatorChromiumTest, setupScrollbarLayerShouldNotCrash)
 {
     registerMockedHttpURLLoad("setup_scrollbar_layer_crash.html");
     navigateTo(m_baseURL + "setup_scrollbar_layer_crash.html");
     // This test document setup an iframe with scrollbars, then switch to
     // an empty document by javascript.
 }
 
 } // namespace