Added a base::Feature command line switch for specifying a clock-drift setup

This CL adds a command line switch based on base::Feature to allow the user
to explicitly specify when the setup used is such that the audio playout and
capture are done on different clocks (has clock-drift).

Bug: chromium:816742
Change-Id: I8a8e15ef479062a0ab30878ef3bde5b5c1f52d6e
Reviewed-on: https://chromium-review.googlesource.com/938921
Commit-Queue: Per Åhgren <peah@chromium.org>
Reviewed-by: Nick Carter <nick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539795}

content/public/common/content_features.cc

@@ -475,6 +475,11 @@ const base::Feature kWebRtcUseEchoCanceller3{"WebRtcUseEchoCanceller3",
 const base::Feature kWebRtcAecBoundedErlSetup{
     "WebRtcAecBoundedErlSetup", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Informs the WebRTC Acoustic Echo Canceler (AEC) that the playout and
+// capture is done using different clocks.
+const base::Feature kWebRtcAecClockDriftSetup{
+    "WebRtcAecClockDriftSetup", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Use GpuMemoryBuffer backed VideoFrames in media streams.
 const base::Feature kWebRtcUseGpuMemoryBufferVideoFrames{
     "WebRTC-UseGpuMemoryBufferVideoFrames", base::FEATURE_DISABLED_BY_DEFAULT};

content/public/common/content_features.h

@@ -114,6 +114,7 @@ CONTENT_EXPORT extern const base::Feature kWebAuth;
 CONTENT_EXPORT extern const base::Feature kWebGLImageChromium;
 CONTENT_EXPORT extern const base::Feature kWebPayments;
 CONTENT_EXPORT extern const base::Feature kWebRtcAecBoundedErlSetup;
+CONTENT_EXPORT extern const base::Feature kWebRtcAecClockDriftSetup;
 CONTENT_EXPORT extern const base::Feature kWebRtcEcdsaDefault;
 CONTENT_EXPORT extern const base::Feature kWebRtcHWH264Encoding;
 CONTENT_EXPORT extern const base::Feature kWebRtcHWVP8Encoding;

content/renderer/media/stream/media_stream_audio_processor.cc

@@ -627,6 +627,8 @@ void MediaStreamAudioProcessor::InitializeAudioProcessingModule(
     webrtc::EchoCanceller3Config aec3_config;
     aec3_config.ep_strength.bounded_erl =
         base::FeatureList::IsEnabled(features::kWebRtcAecBoundedErlSetup);
+    aec3_config.echo_removal_control.has_clock_drift =
+        base::FeatureList::IsEnabled(features::kWebRtcAecClockDriftSetup);
 
     ap_builder.SetEchoControlFactory(
         std::unique_ptr<webrtc::EchoControlFactory>(