Added volume adjust sound behind the flag. Partially based on https://codereview.chromium.org/24618003/.

BUG=225886
TEST=media_unittests:AudioStreamHandler*

Review URL: https://codereview.chromium.org/115693004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245342 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245342