Hook PushMessagingMessageFilter up to GCMDriver
Add plumbing for registration from push service-agnostic content layer
to GCMDriver in chrome layer.
To achieve this, GCMProfileService owns an implementation of a new
PushMessagingService class, which can be used from the content layer.
Based on mvanouwerkerk's prototype in https://codereview.chromium.org/
186023002, but significantly refactored.
BUG=350384
TBR=benm@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=276792
Review URL: https://codereview.chromium.org/
317823007
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@277016 0039d316-1c4b-4281-b951-d872f2087c98