Adding functionality for activating for the WebRTC EchoCanceller3 functionality in Chrome.

content/renderer/media/media_stream_audio_processor.cc

Index: content/renderer/media/media_stream_audio_processor.cc
diff --git a/content/renderer/media/media_stream_audio_processor.cc b/content/renderer/media/media_stream_audio_processor.cc
index 6f7afe612a4a9d74c9cf555243ed1840be176828..d45605eb18bc3f5b8f08126a73fb4f5c13be6196 100644
--- a/content/renderer/media/media_stream_audio_processor.cc
+++ b/content/renderer/media/media_stream_audio_processor.cc
@@ -580,6 +580,11 @@ void MediaStreamAudioProcessor::GetStats(AudioProcessorStats* stats) {
   GetAudioProcessingStats(audio_processing_.get(), stats);
 }
 
+// Features for http://crbug.com/688388. This value is sent to WebRTC's echo

[hlundin-chromium, 2017/02/09 10:20:45]

Move this information to content_features.{h|cc}.

[peah, 2017/02/15 13:24:24]

Done.

+// canceller to toggle which echo canceller should be used.
+const base::Feature kUseEchoCanceller3{"UseEchoCanceller3",

[hlundin-chromium, 2017/02/09 10:20:45]

You are defining this feature twice: here and in content_features.{h,cc}. I
think the pattern is to use one of them. I can only guess that you must define
it in content_features in order to connect it to chrome://flags, which means you
should delete this one. Instead, you will have to include
#include "content/public/common/content_features.h"
in this file.

[peah, 2017/02/15 13:24:24]

Thanks! Great suggestion!

Done.

+                                       base::FEATURE_DISABLED_BY_DEFAULT};
+
 void MediaStreamAudioProcessor::InitializeAudioProcessingModule(
     const blink::WebMediaConstraints& constraints,
     const MediaStreamDevice::AudioDeviceParameters& input_params) {
@@ -676,6 +681,11 @@ void MediaStreamAudioProcessor::InitializeAudioProcessingModule(
     // Prepare for logging echo information. If there are data remaining in
     // |echo_information_| we simply discard it.
     echo_information_.reset(new EchoInformation());
+
+    apm_config.echo_canceller3.enabled =
+        base::FeatureList::IsEnabled(kUseEchoCanceller3);
+  } else {
+    apm_config.echo_canceller3.enabled = false;
   }
 
   if (goog_ns) {