Wire up the MediaStreamAudioProcessor with the WebRtcAudioCapturer.

This CL is a follow up to https://codereview.chromium.org/88513002, which is hooking up the MediaStreamAudioProcessor to the production code. With this CL, we move the audio processing from WebRtc to Chrome behind a flag. 

When chrome is launched with flag enable-audio-track-processing, the audio processing in happening in the WebRtcAudioCapturer, otherwise it will be in WebRtc, which is the same as without this CL.

Theoretically, we should be able to apply different constraints on different audio tracks, that means there can be multiple audio processors with different configurations for different tracks. But this can't be done before we completely move the audio processing to Chrome. So this CL has only one processor in the WebRtcAudioCapturer. Note that this is not a regression since our code has been behaving like this before this CL.
 
 
BUG=264611
TEST= content_unittest && ./chrome --enable-audio-track-processing works with audio processing.

Review URL: https://codereview.chromium.org/112203004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244992 0039d316-1c4b-4281-b951-d872f2087c98
20 files changed