Implemented WebRTC-AppRTC integration test.

This test will require a special gclient solution (implemented here:
https://codereview.chromium.org/25857002/) which will download the latest
apprtc code and the google appengine SDK. Then, it will launch a local
appengine instance and verify we can get an AppRTC call up on that by
connecting with two browser tabs.

This provides a hermetic integration test for WebRTC-AppRTC which should
be quite stable - it doesn't involve any connections to external servers.

BUG=303021
R=xians@chromium.org

Review URL: https://codereview.chromium.org/25652003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228053 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228053