Pyauto test for Google Talk Extension. Also add test to chrome pyauto test suite to run with chrome continuous build.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=123296

Review URL: https://chromiumcodereview.appspot.com/9317067
Patch from Jeanne Qian <jqian@google.com>.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@123303 0039d316-1c4b-4281-b951-d872f2087c98