Propagate muted state from MediaStreamAudioSource into JS.

third_party/WebKit/Source/modules/mediastream/MediaStreamTrack.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  * Copyright (C) 2011 Ericsson AB. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 46 matching lines @@
 }  // namespace
 
 MediaStreamTrack* MediaStreamTrack::Create(ExecutionContext* context,
                                            MediaStreamComponent* component) {
   return new MediaStreamTrack(context, component);
 }
 
 MediaStreamTrack::MediaStreamTrack(ExecutionContext* context,
                                    MediaStreamComponent* component)
     : ContextLifecycleObserver(context),
-      ready_state_(MediaStreamSource::kReadyStateLive),
+      ready_state_(component->Source()->GetReadyState()),
       is_iterating_registered_media_streams_(false),
       stopped_(false),
       component_(component),
       // The source's constraints aren't yet initialized at creation time.
       constraints_() {
   component_->Source()->AddObserver(this);
 
+  // If the source is already non-live at this point, the observer won't have
+  // been called. Check the muted state manually.
+  if (ready_state_ == MediaStreamSource::kReadyStateMuted)

[miu, 2017/06/19 19:40:37]

This code assumes MediaStreamComponent::muted_ is always false at this point.
However, this is not guaranteed (see the MSC ctor).

Suggest making this an unconditional call:

  component_->SetMuted(ready_state_ == MediaStreamSource::kReadyStateMuted);

[ossu-chromium, 2017/06/26 16:06:14]

From what I could gather, that constructor is (un?)fortunately never called with
muted set to anything but false. However, I think your suggestion makes a lot of
sense. Will change!

+    component_->SetMuted(true);
+
   if (component_->Source() &&
       component_->Source()->GetType() == MediaStreamSource::kTypeVideo) {
     // ImageCapture::create() only throws if |this| track is not of video type.
     NonThrowableExceptionState exception_state;
     image_capture_ = ImageCapture::Create(context, this, exception_state);
   }
 }
 
 MediaStreamTrack::~MediaStreamTrack() {}
 
@@ skipping 91 matching lines @@
       }
   }
 
   component_->SetContentHint(translated_hint);
 }
 
 String MediaStreamTrack::readyState() const {
   if (Ended())
     return "ended";
 
+  // Although muted is tracked as a ReadyState, only "live" and "ended" are
+  // visible externally.
   switch (ready_state_) {
     case MediaStreamSource::kReadyStateLive:
+    case MediaStreamSource::kReadyStateMuted:
       return "live";
-    case MediaStreamSource::kReadyStateMuted:
-      return "muted";
     case MediaStreamSource::kReadyStateEnded:
       return "ended";
   }
 
   NOTREACHED();
   return String();
 }
 
 void MediaStreamTrack::stopTrack(ExceptionState& exception_state) {
   if (Ended())
     return;
 
   ready_state_ = MediaStreamSource::kReadyStateEnded;

[miu, 2017/06/19 19:40:37]

Assigning to |ready_state_| here could be dangerous: What prevents a future call
to SourceChangedState() from changing it to something else?

[ossu-chromium, 2017/06/26 16:06:14]

There's an if (Ended()) clause in SourceChangedState as well, which would stop
any future changes once we get to ended.

   MediaStreamCenter::Instance().DidStopMediaStreamTrack(Component());
   DispatchEvent(Event::Create(EventTypeNames::ended));
   PropagateTrackEnded();
 }
 
 MediaStreamTrack* MediaStreamTrack::clone(ScriptState* script_state) {
   // TODO(pbos): Make sure m_readyState and m_stopped carries over on cloned
   // tracks.
   MediaStreamComponent* cloned_component = Component()->Clone();
   MediaStreamTrack* cloned_track = MediaStreamTrack::Create(
@@ skipping 195 matching lines @@
 
 DEFINE_TRACE(MediaStreamTrack) {
   visitor->Trace(registered_media_streams_);
   visitor->Trace(component_);
   visitor->Trace(image_capture_);
   EventTargetWithInlineData::Trace(visitor);
   ContextLifecycleObserver::Trace(visitor);
 }
 
 }  // namespace blink