Wires up MotionEvents for mojo_shell_apk on Android.

Receive Touch and Trackball events from our MojoViewport View and send them via NativeViewport to sample_app.
Note that I do not support multiple touchpoints right now. This is something I can easily add later but decided to start here.

BUG=
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/63493002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233716 0039d316-1c4b-4281-b951-d872f2087c98
[GCM] Add GCMClient interface and dummy implementation

BUG=284553
TEST=none due to no real implementation added yet
R=fgorski@chromium.org, zea@chromium.org

Review URL: https://codereview.chromium.org/62803002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233717 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233716
SVN changes up to revision 233717