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..231eafe635e107e8a713a90cbb446d01f5446255 100644
--- a/content/renderer/media/media_stream_dependency_factory.cc
+++ b/content/renderer/media/media_stream_dependency_factory.cc
@@ -96,6 +96,40 @@ void ApplyFixedAudioConstraints(RTCMediaConstraints* constraints) {
   }
 }
 
+void TransferConstraintToPlatformEffect(RTCMediaConstraints* constraints,
+                                        const char* key,
+                                        bool* platform_effect) {
+  bool value;
+  if (!webrtc::FindConstraint(constraints, key, &value, NULL) ||
+      value == false) {
+    // If the constraint does not exist, or is set to false, disable the
+    // corresponding platform effect.
+    *platform_effect = false;
+    DVLOG(1) << "Disabling platform effect: " << key;
+  } else {
+    if (*platform_effect) {
+      // If the constraint is set to true, and the corresponding platform effect
+      // is available, disable the constraint.
+      constraints->AddMandatory(key,
+          webrtc::MediaConstraintsInterface::kValueFalse, true);
+      DVLOG(1) << "Disabling constraint: " << key;
+    }
+  }
+}
+
+// Any true constraint with an available corresponding platform effect will be
+// set to false. Any false constraint will cause the corresponding platform
+// effect to be disabled.
+//
+// This currently only deals with AEC, but is prepared for expansion to other
+// platform effects.
+void TransferConstraintsToPlatformEffects(RTCMediaConstraints* constraints,
+    MediaStreamDevice::AudioDeviceParameters* params) {
+  TransferConstraintToPlatformEffect(constraints,
+      webrtc::MediaConstraintsInterface::kEchoCancellation,
+      &params->use_platform_aec);
+}
+
 class P2PPortAllocatorFactory : public webrtc::PortAllocatorFactoryInterface {
  public:
   P2PPortAllocatorFactory(
@@ -323,7 +357,17 @@ 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 platform_constraints = native_audio_constraints;
+    // This causes constraint settings to be transferred to their corresponding
+    // platform effects. For example, if a platform AEC is available, and the
+    // AEC constraint is set to true, we should leave the platform AEC
+    // enabled, and disable the software AEC by setting the constraint to false.
+    // Contrariwise, if the AEC constraint is set to false, we should disable
+    // the platform AEC even if available.
+    TransferConstraintsToPlatformEffects(&platform_constraints,
+                                         &device_info.device.input);
     scoped_refptr<WebRtcAudioCapturer> capturer(
         MaybeCreateAudioCapturer(render_view_id, device_info));
     if (!capturer.get()) {
@@ -341,7 +385,7 @@ 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(&platform_constraints).get());
     source_observer->AddSource(source_data->local_audio_source());
   }
 
@@ -910,7 +954,8 @@ 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.use_platform_aec)) {
     return NULL;
   }