Currently, the MediaPlayerRenderer does not allow authenticated
playback.

This change adds the necessary plumbing to send the first party URL
from blink::WebLocalFrame to the MediaPlayerBridge, in order to access
(or to be denied access to) the first party cookies.

Also opened 659826 which might necessite further investigation.

BUG=636604
TEST=updated UTs for MediaUrlDemuxer

Review-Url: https://codereview.chromium.org/2434413002
Cr-Commit-Position: refs/heads/master@{#427924}