Add support for notifying about refreshed credentials.
Currently the Android platform does not inform the native code
that new credentials are available. This CL adds the necessary
functionality to fire the required notifications.
* Adds a Java instance of the OAuth2TokenService.
* Adds FireRefreshTokenAvailable().
* Adds support for Java-based observers.
* Adds a BroadcastReceiver to trigger the notification for the
Chrome Shell.
BUG=302143
Review URL: https://codereview.chromium.org/
25653003
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228104 0039d316-1c4b-4281-b951-d872f2087c98