Fix video to canvas copying with display lists enabled

Short term fix: destination canvas falls out of display list mode
when a video is drawn to it. Follow-up work is necessary to
support accelerated video decoding with inter-context SkPicture sharing

BUG=428509
TEST=fast/canvas/canvas-drawImage-video.html

Review URL: https://codereview.chromium.org/692673002

git-svn-id: svn://svn.chromium.org/blink/trunk@184616 bbb929c8-8fbe-4397-9dbb-9b2b20218538