HTMLMediaElement capture: teach the captured MStream to follow up source events

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

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  * Copyright (C) 2011, 2012 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 313 matching lines @@
     UseCounter::count(getExecutionContext(), UseCounter::MediaStreamOnInactive);
 
   return EventTargetWithInlineData::addEventListenerInternal(eventType,
                                                              listener, options);
 }
 
 const AtomicString& MediaStream::interfaceName() const {
   return EventTargetNames::MediaStream;
 }
 
-void MediaStream::addRemoteTrack(MediaStreamComponent* component) {
+void MediaStream::addTrackByComponent(MediaStreamComponent* component) {
   DCHECK(component);
   if (!getExecutionContext())
     return;
 
   MediaStreamTrack* track =
       MediaStreamTrack::create(getExecutionContext(), component);
   switch (component->source()->type()) {
     case MediaStreamSource::TypeAudio:
       m_audioTracks.push_back(track);
       break;
     case MediaStreamSource::TypeVideo:
       m_videoTracks.push_back(track);
       break;
   }
   track->registerMediaStream(this);
   m_descriptor->addComponent(component);
 
   scheduleDispatchEvent(
       MediaStreamTrackEvent::create(EventTypeNames::addtrack, track));
 
   if (!active() && !track->ended()) {
     m_descriptor->setActive(true);
     scheduleDispatchEvent(Event::create(EventTypeNames::active));
   }
 }
 
-void MediaStream::removeRemoteTrack(MediaStreamComponent* component) {
+void MediaStream::removeTrackByComponent(MediaStreamComponent* component) {

[haraken, 2017/03/06 18:37:29]

I'm just curious: What happens if ExecutionContext gets detached after we called
addTrackByComponent but before we call removeTrackByComponent? Then
getExecutionContext() will return false at line 363 and thus the following code
won't run. Will it be okay?

[mcasas, 2017/03/06 19:38:59]

I'm not sure what the original developers intended,
perhaps we should also destroy the MediaStream if
and when the context is lost, but we are not a 
ContextLifecycleObserver, so I guess we're fine just
doing nothing?  
+guidou@ any thoughts?

   DCHECK(component);
   if (!getExecutionContext())
     return;
 
   MediaStreamTrackVector* tracks = 0;
   switch (component->source()->type()) {
     case MediaStreamSource::TypeAudio:
       tracks = &m_audioTracks;
       break;
     case MediaStreamSource::TypeVideo:
@@ skipping 58 matching lines @@
   EventTargetWithInlineData::trace(visitor);
   ContextClient::trace(visitor);
   MediaStreamDescriptorClient::trace(visitor);
 }
 
 MediaStream* toMediaStream(MediaStreamDescriptor* descriptor) {
   return static_cast<MediaStream*>(descriptor->client());
 }
 
 }  // namespace blink