Enable platform echo cancellation through the AudioRecord path.

content/renderer/media/media_stream_dependency_factory.cc

Index: content/renderer/media/media_stream_dependency_factory.cc
diff --git a/content/renderer/media/media_stream_dependency_factory.cc b/content/renderer/media/media_stream_dependency_factory.cc
index 6172e06a8e31da352c32b056fc1cf6585ef2dcc6..8da7b14cb7120cc0a1d05b5b84c2414896d433fa 100644
--- a/content/renderer/media/media_stream_dependency_factory.cc
+++ b/content/renderer/media/media_stream_dependency_factory.cc
@@ -78,6 +78,15 @@ struct {
     webrtc::MediaConstraintsInterface::kValueTrue },
 };
 
+// Map of corresponding media constraints and platform effects.
+struct {
+  const char* constraint;
+  const media::AudioParameters::PlatformEffectsMask effect;
+} const kConstraintEffectMap[] = {
+  { webrtc::MediaConstraintsInterface::kEchoCancellation,
+    media::AudioParameters::ECHO_CANCELLER},
+};
+
 // Merge |constraints| with |kDefaultAudioConstraints|. For any key which exists
 // in both, the value from |constraints| is maintained, including its
 // mandatory/optional status. New values from |kDefaultAudioConstraints| will
@@ -323,7 +332,36 @@ void MediaStreamDependencyFactory::CreateNativeMediaSources(
 
     // TODO(xians): Create a new capturer for difference microphones when we
     // support multiple microphones. See issue crbug/262117 .
-    const StreamDeviceInfo device_info = source_data->device_info();
+    StreamDeviceInfo device_info = source_data->device_info();
+    RTCMediaConstraints constraints = native_audio_constraints;
+
+    // If any platform effects are available, check them against the
+    // constraints. Disable effects to match false constraints, but if a
+    // constraint is true, set the constraint to false to later disable the
+    // software effect.
+    int effects = device_info.device.input.effects;
+    if (effects != media::AudioParameters::NO_EFFECTS) {
+      for (size_t i = 0; i < ARRAYSIZE_UNSAFE(kConstraintEffectMap); ++i) {
+        bool value;
+        if (!webrtc::FindConstraint(&constraints,
+                kConstraintEffectMap[i].constraint, &value, NULL) || !value) {
+          // If the constraint is false, or does not exist, disable the platform
+          // effect.
+          effects &= ~kConstraintEffectMap[i].effect;
+          DVLOG(1) << "Disabling constraint: "
+                   << kConstraintEffectMap[i].constraint;
+        } else if (effects & kConstraintEffectMap[i].effect) {
+          // If the constraint is true, leave the platform effect enabled, and
+          // set the constraint to false to later disable the software effect.
+          constraints.AddMandatory(kConstraintEffectMap[i].constraint,
+              webrtc::MediaConstraintsInterface::kValueFalse, true);
+          DVLOG(1) << "Disabling platform effect: "
+                   << kConstraintEffectMap[i].constraint;
+        }
+      }
+      device_info.device.input.effects = effects;
+    }
+
     scoped_refptr<WebRtcAudioCapturer> capturer(
         MaybeCreateAudioCapturer(render_view_id, device_info));
     if (!capturer.get()) {
@@ -341,7 +379,7 @@ void MediaStreamDependencyFactory::CreateNativeMediaSources(
     // Creates a LocalAudioSource object which holds audio options.
     // TODO(xians): The option should apply to the track instead of the source.
     source_data->SetLocalAudioSource(
-        CreateLocalAudioSource(&native_audio_constraints).get());
+        CreateLocalAudioSource(&constraints).get());

[no longer working on chromium, 2013/12/30 14:55:56]

you modify the constraints and save the change in the audio options owned by the
LocalAudioSource, but the change is not known by other classes which use the
constraints, for example, WebRtcLocalAudioTrack.

[ajm, 2014/01/08 01:35:02]

We only need to update the constraints for paths which will be processing the
input audio. Does WebRtcLocalAudioTrack (or any other path) do that?

     source_observer->AddSource(source_data->local_audio_source());
   }
 
@@ -910,7 +948,8 @@ MediaStreamDependencyFactory::MaybeCreateAudioCapturer(
           device_info.session_id,
           device_info.device.id,
           device_info.device.matched_output.sample_rate,
-          device_info.device.matched_output.frames_per_buffer)) {
+          device_info.device.matched_output.frames_per_buffer,
+          device_info.device.input.effects)) {
     return NULL;
   }