Make MediaFilter::Stop() asynchronous.

This is the second issue regarding making Stop() asynchronous.

All Stop() in subclasses of MediaFilter is made to accept a callback and
runs the callback at the end of its stop.

BUG=16059
TEST=media_unittest, unit_tests, test_shell_tests still passes

Review URL: http://codereview.chromium.org/2541003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@49548 0039d316-1c4b-4281-b951-d872f2087c98
29 files changed