Remove mojom cpp and JS generators and turn on the jinja generator for both.

BUG=329008

Review URL: https://codereview.chromium.org/104503013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241793 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241793