Do not use composited scrolling with clip paths

This is currently busted in cc. For now, let's disable compositor driven
scrolling in this case.

Review URL: https://codereview.chromium.org/360523002

git-svn-id: svn://svn.chromium.org/blink/trunk@178103 bbb929c8-8fbe-4397-9dbb-9b2b20218538