Kill ImmersiveFullscreenConfiguration and remove flags for disabling immersive fullscreen

BUG=307622
TEST=None
R=jamescook
TBR=sky (For removal of ImmersiveFullscreenConfiguration in tests and straightforward revert of https://codereview.chromium.org/14622007)

Review URL: https://codereview.chromium.org/33273005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230525 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230525