Don't exit full-screen mode when the Escape key is pressed for apps v2.

BUG=341539
R=garykac@chromium.org

Review URL: https://codereview.chromium.org/138783009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249509 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249509