Fixed the problem where audio processing is disabled when video effect is enabled.
And added unittest to prevent such problems happening again.


BUG=324293
TEST=content_unittests --gtest_filter="*WebRtcAudioCapturer*"

Review URL: https://codereview.chromium.org/95083002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237861 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237861