Set up clip and scroll parents on the blink side.

Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 3952 matching lines @@
             m_client->didDeactivateCompositor();
             m_compositorCreationFailed = true;
         }
     }
     if (page())
         page()->mainFrame()->view()->setClipsRepaints(!m_isAcceleratedCompositingActive);
 }
 
 void WebViewImpl::updateMainFrameScrollPosition(const IntPoint& scrollPosition, bool programmaticScroll)
 {
+    TRACE_EVENT1("impl-scroll",

[enne (OOO), 2013/08/22 20:54:30]

Should this go after the early outs?

+        "WebViewImpl::updateMainFrameScrollPosition",
+        "programmatic", programmaticScroll);
+
     FrameView* frameView = page()->mainFrame()->view();
     if (!frameView)
         return;
 
     if (frameView->scrollPosition() == scrollPosition)
         return;
 
     bool oldProgrammaticScroll = frameView->inProgrammaticScroll();
     frameView->setInProgrammaticScroll(programmaticScroll);
     frameView->notifyScrollPositionChanged(scrollPosition);
     frameView->setInProgrammaticScroll(oldProgrammaticScroll);
 }
 
 void WebViewImpl::applyScrollAndScale(const WebSize& scrollDelta, float pageScaleDelta)
 {
     if (!mainFrameImpl() || !mainFrameImpl()->frameView())
         return;
 
     if (pageScaleDelta == 1) {
-        TRACE_EVENT_INSTANT2("webkit", "WebViewImpl::applyScrollAndScale::scrollBy", "x", scrollDelta.width, "y", scrollDelta.height);
+        TRACE_EVENT_INSTANT2("webkit,impl-scroll", "WebViewImpl::applyScrollAndScale::scrollBy", "x", scrollDelta.width, "y", scrollDelta.height);

[enne (OOO), 2013/08/22 20:54:30]

Aren't you tracing updateMainFrameScrollPosition too? There's lots of trace
events here that all seem to be doing the same thing.  I'm not sure what this is
gaining, other than really deep redundant traces.

         WebSize webScrollOffset = mainFrame()->scrollOffset();
         IntPoint scrollOffset(webScrollOffset.width + scrollDelta.width, webScrollOffset.height + scrollDelta.height);
         updateMainFrameScrollPosition(scrollOffset, false);
     } else {
         // The page scale changed, so apply a scale and scroll in a single
         // operation.
         WebSize scrollOffset = mainFrame()->scrollOffset();
         scrollOffset.width += scrollDelta.width;
         scrollOffset.height += scrollDelta.height;
 
@@ skipping 121 matching lines @@
 }
 
 bool WebViewImpl::shouldDisableDesktopWorkarounds()
 {
     ViewportArguments arguments = mainFrameImpl()->frame()->document()->viewportArguments();
     return arguments.width == ViewportArguments::ValueDeviceWidth || !arguments.userZoom
         || (arguments.minZoom == arguments.maxZoom && arguments.minZoom != ViewportArguments::ValueAuto);
 }
 
 } // namespace WebKit