Add GCM to the Google Play Services Library.

Cacheinvalidation uses GCM for sending messages on Android. It currently
uses the deprecated GCM client library and is being updated to depend on
the GCM split in Google Play Services.

Also removing the unused classes being added for Auth.

BUG=397327

Change-Id: I4375c5e3c0e5862d5e6769b2a6a2ec2adcc9af80
Reviewed-on: https://chromium-review.googlesource.com/293650
Reviewed-by: Armand Navabi <navabi@chromium.org>
Commit-Queue: Armand Navabi <navabi@chromium.org>
Tested-by: Armand Navabi <navabi@chromium.org>