Reviewed by Darin Adler.

        Artifacts when scrolling with new drawing area
        https://bugs.webkit.org/show_bug.cgi?id=52682

        * WebProcess/WebCoreSupport/WebChromeClient.cpp:
        (WebKit::WebChromeClient::scroll):
        When scrolling, we want the intersection of the scroll rect and clip rect.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@76085 268f45cc-cd09-0410-ab3c-d52691b4dbfc