Fix a problem that fullscreen controller will show up if a page has multiple videos

When video metadata from another video is extracted, we should not update the metadata of the fullscreen video.
We should only update the metadata if the player is fullscreen player

TBR=michaelbai
BUG=321213

Review URL: https://codereview.chromium.org/80423004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236608 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236608