Ensures that AudioMessageFilter now lives on the main render thread.

In addition, removes usage of routing ID by utilizing control messages instead of routed messages.

BUG=none
TESTS=none
Review URL: http://codereview.chromium.org/7157001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@92138 0039d316-1c4b-4281-b951-d872f2087c98
27 files changed