Wire up AGC to the MediaStreamAudioProcessor.

This CL enables the AGC in the processor based on the constraints, and also trigger SetVolume() in the capturer if the AGC tries to adjust the volume.

There are also some small changes in the MediaStreamAudioProcessor and its unittest.

BUG=264611
TEST= content_unittest --gtest_filter="*MediaStreamAudioProcessor*"

Review URL: https://codereview.chromium.org/141513006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246894 0039d316-1c4b-4281-b951-d872f2087c98
6 files changed