Cast: Wire up sending status log messages from sender to receiver.

Includes both handling of the received message in the receiver and
sending the message in the sender. The acctual packeiztion and parser
has been landed in prior CLs.

Review URL: https://codereview.chromium.org/105883010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240122 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240122