Fix media/video expectations to need rebaseline for composited video.

TBR=scherkus
BUG=365857

Review URL: https://codereview.chromium.org/449473004

git-svn-id: svn://svn.chromium.org/blink/trunk@179625 bbb929c8-8fbe-4397-9dbb-9b2b20218538