Set up clip and scroll parents on the blink side.

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index 0fc79df8a17a0925508dfff0ed5945cd5d88150c..68536e61e53a3bab483683e99b320fb499c712d4 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -3970,6 +3970,10 @@ void WebViewImpl::setIsAcceleratedCompositingActive(bool active)
 
 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;
@@ -3989,7 +3993,7 @@ void WebViewImpl::applyScrollAndScale(const WebSize& scrollDelta, float pageScal
         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);