enable subtitle support and the new fullscreen video

This CL enables the subtitle and new fullscreen video for chrome.
The new fullscreen mode has been in testing for a while, this Cl will enable this new fullscreen mode.

BUG=262945

Review URL: https://codereview.chromium.org/182493003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255500 0039d316-1c4b-4281-b951-d872f2087c98
Docserver: Correctly disambiguate between what 'platform' means in a features
file.

BUG=350057
R=yoz@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/189123002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255501 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255500
aw: Remove kDisableSimpleCache switch

Simple cache has been shipping on android stable for a few releases now.
No need to have switch to disable it.

BUG=350143
NOTRY=true

Review URL: https://codereview.chromium.org/187693009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255502 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255502