Coordinated Graphics: Handle scrolling correctly.
https://bugs.webkit.org/show_bug.cgi?id=111406

Patch by Huang Dongsung <luxtella@company100.net> on 2013-03-08
Reviewed by Simon Fraser.

Coordinated Graphics deals with fast scrolling and slow scrolling in the same
routine, so WebChromeClient::invalidateContentsForSlowScroll() should call
DrawingArea:scroll().

When CoordinatedLayerTreeHost::scrollNonCompositedContents() is called, we
should call scheduleLayerFlush() to notify to UI Process. In addition, when we
don't use fixed layout, we should call setNonCompositedContentsNeedDisplay() to
update non composited contents.

* WebProcess/WebCoreSupport/WebChromeClient.cpp:
(WebKit::WebChromeClient::invalidateContentsForSlowScroll):
* WebProcess/WebPage/CoordinatedGraphics/CoordinatedLayerTreeHost.cpp:
(WebKit::CoordinatedLayerTreeHost::scrollNonCompositedContents):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@145230 268f45cc-cd09-0410-ab3c-d52691b4dbfc