Canvas: composite video on canvas correctly.

Currently, 2D Canvas composites a video as only source-over,
because Blink doesn't pass composite information to chromium
when calling platform video painting API.
This CL fixes it.

TEST=fast/canvas/canvas-drawImage-video.html
BUG=407079

Review URL: https://codereview.chromium.org/443873005

git-svn-id: svn://svn.chromium.org/blink/trunk@181175 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[ServiceWorker] Support setting body to Request object in ServiceWorker.

BUG=402387
TEST=run_webkit_tests http/tests/serviceworker/request.html

Review URL: https://codereview.chromium.org/516603004

git-svn-id: svn://svn.chromium.org/blink/trunk@181176 bbb929c8-8fbe-4397-9dbb-9b2b20218538