aura/cc: clip webkit layer size to external texture dimensions
aura/cc: clip webkit layer size to external texture dimensions

This maps the behavior of the old compositor.

BUG=None
TEST=Resize window with accelerated content. Observe no "trailing" of the content on the borders.


Review URL: http://codereview.chromium.org/8590021

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@110512 0039d316-1c4b-4281-b951-d872f2087c98

adobe/chromium,ropik/chromium,gavinp/chromium,gavinp/chromium,gavinp/chromium,yitian134/chromium,ropik/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,gavinp/chromium,ropik/chromium,ropik/chromium,ropik/chromium,yitian134/chromium,adobe/chromium,ropik/chromium,adobe/chromium,gavinp/chromium,adobe/chromium,gavinp/chromium,ropik/chromium,adobe/chromium,ropik/chromium,yitian134/chromium,gavinp/chromium,yitian134/chromium,adobe/chromium,yitian134/chromium,yitian134/chromium,yitian134/chromium,yitian134/chromium,adobe/chromium,yitian134/chromium,adobe/chromium,adobe/chromium,gavinp/chromium,gavinp/chromium,adobe/chromium,adobe/chromium