[Android] Reverse the enable-cast flag to turn the feature on by default in dev builds.

NOTRY=true
BUG=None

Review URL: https://codereview.chromium.org/177373004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252912 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252912