Remove unused code calling WebMediaPlayerClient::requestFullscreen()

This was used for a while and then removed again:
https://codereview.chromium.org/41123002
https://codereview.chromium.org/1021723003

BUG=496627

Review URL: https://codereview.chromium.org/1156273006

Cr-Commit-Position: refs/heads/master@{#334132}
9 files changed