am "am c9b5f98b: am 6f5d4bd8: am de91b384: am e385672c: docs: remove reference to GCM doc from C2DM doc"

merged from goog/mirror-m-wireless-internal-release
04cfeb3 am c9b5f98b: am 6f5d4bd8: am de91b384: am e385672c: docs: remove reference to GCM doc from C2DM doc