[GCM] Only allow the senders that the application is currently registered for

[GCM] Only allow the senders that the application is currently registered for

Only allow the senders that the application is currently registered for to send messages to it.

* GCMProfileService adds a check that the app is currently registered for the sender_id of the sender that sent the message
* IncomingMessage is extended to add sender_id
* GCMClientImpl adds the sender_id to the incoming message in the handling code.
* Adding a test verifying that messages are not delivered when not registered for senders
* fixing the GCM Profile Service tests that were previously not registering for senders before delivering messages

* Also: moving the DCHECKS in the GCMClientImpl::HandleIncomingMessage higher up to run them as soon as the checks values are available.

BUG=344665

[fgorski, 2014-03-03 19:36:18]

PTAL.

This patch depends on https://codereview.chromium.org/183923006/ --- the single
sender only change.

[Dmitry Titov, 2014-03-03 20:02:37]

LGTM assuming the "single sender" goes first :-)

[jianli, 2014-03-04 01:14:54]

Please re-upload the patch due to missing side-by-side differences.

[fgorski, 2014-03-05 00:32:19]

Obsoleted by https://codereview.chromium.org/185133008/