New pyauto translate hooks: always and never translate button.

This hooks allows testers to test that always and never translate button that shows up after a user has accepted/declined translation several times.

Review URL: http://codereview.chromium.org/3061054

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@55590 0039d316-1c4b-4281-b951-d872f2087c98