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. 

This CL obsoletes https://codereview.chromium.org/185933003/

BUG=344665

Review URL: https://codereview.chromium.org/185133008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255483 0039d316-1c4b-4281-b951-d872f2087c98
Remove --disable-accelerated-plugins flag

BUG=None

Review URL: https://codereview.chromium.org/188113002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255484 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255483
SVN changes up to revision 255484