GitLab

This patch provides the minimal changes necessary to hook
WebMediaPlayerImpl into HTMLDocumentView so that <audio>/<video> tags
work. HTMLMediaElement will now function, but audio won't be audible
right now. Proper audio output will be added in a followup patch.

Review URL: https://codereview.chromium.org/567803002

Cr-Commit-Position: refs/heads/master@{#294692}