GitLab

Removed the toggle between Presentation Mode and Fullscreen.
Renamed UpdateFullscreenWithToolbar to UpdateUIForTabFullscreen.
Fixed the fullscreen toolbar logic in BWC so that the toolbar state is
correct when we exit tab fullscreen.

BUG=579259

Review-Url: https://codereview.chromium.org/2089323002
Cr-Commit-Position: refs/heads/master@{#402677}