Create a private API for controlling WebRTC's AEC3

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 46d742807bd5c20e4b6fba0bb13223cea158244d..484cd3f2270c0e443970d713362ea6de82d43f9d 100644
--- a/content/renderer/media/media_stream_audio_processor.cc
+++ b/content/renderer/media/media_stream_audio_processor.cc
@@ -486,6 +486,23 @@ void MediaStreamAudioProcessor::OnDisableAecDump() {
     StopEchoCancellationDump(audio_processing_.get());
 }
 
+void MediaStreamAudioProcessor::OnAec3Enable(bool enable) {
+  DCHECK(main_thread_runner_->BelongsToCurrentThread());
+  if (override_aec3_ != base::Optional<bool>(enable)) {

[Henrik Grunell, 2017/04/10 08:13:28]

Early returns instead in this function, e.g.

if (override_aec3_ == base::Optional<bool>(enable))
  return;

...

[hlundin-chromium, 2017/04/10 10:10:16]

Done.

+    override_aec3_ = base::Optional<bool>(enable);
+    if (has_echo_cancellation_) {
+      DCHECK(audio_processing_);

[Henrik Grunell, 2017/04/10 08:13:28]

Remove (redundant). It will crash on the next line if not set.

[hlundin-chromium, 2017/04/10 10:10:16]

Done.

+      auto apm_config = audio_processing_->GetConfig();
+      if (apm_config.echo_canceller3.enabled != enable) {
+        apm_config.echo_canceller3.enabled = enable;

[Henrik Grunell, 2017/04/10 08:13:28]

I'm not sure how this is supposed to work. If not overridden, should it not go
back to  the features::kWebRtcUseEchoCanceller3 value?

[hlundin-chromium, 2017/04/10 10:10:16]

If not overridden, it will already be at the value determined by
features::kWebRtcUseEchoCanceller3.

[Henrik Grunell, 2017/04/10 12:33:47]

I realized that it can never be un-overridden. Setting it via the API means that
it overrides. Fine.

+        audio_processing_->ApplyConfig(apm_config);
+        DCHECK(echo_information_);
+        echo_information_.reset(new EchoInformation());
+      }
+    }
+  }
+}
+
 void MediaStreamAudioProcessor::OnIpcClosing() {
   DCHECK(main_thread_runner_->BelongsToCurrentThread());
   aec_dump_message_filter_ = NULL;
@@ -596,6 +613,7 @@ void MediaStreamAudioProcessor::InitializeAudioProcessingModule(
 
   const bool echo_cancellation =
       audio_constraints.GetEchoCancellationProperty();
+  has_echo_cancellation_ = echo_cancellation;
   const bool goog_agc = audio_constraints.GetGoogAutoGainControl();
 
 #if defined(OS_ANDROID)
@@ -680,7 +698,9 @@ void MediaStreamAudioProcessor::InitializeAudioProcessingModule(
     echo_information_.reset(new EchoInformation());
 
     apm_config.echo_canceller3.enabled =
-        base::FeatureList::IsEnabled(features::kWebRtcUseEchoCanceller3);
+        override_aec3_
+            ? *override_aec3_
+            : base::FeatureList::IsEnabled(features::kWebRtcUseEchoCanceller3);
   } else {
     apm_config.echo_canceller3.enabled = false;
   }