MediaRecorder: make MediaRecorderHandler a MediaStreamObserver

content/renderer/media/media_recorder_handler.cc

Index: content/renderer/media/media_recorder_handler.cc
diff --git a/content/renderer/media/media_recorder_handler.cc b/content/renderer/media/media_recorder_handler.cc
index 81306935488eaec1062fc0981dc02d6d53baef77..5438f9cedda522555e77ed3300b6779b3853296d 100644
--- a/content/renderer/media/media_recorder_handler.cc
+++ b/content/renderer/media/media_recorder_handler.cc
@@ -93,10 +93,13 @@ bool MediaRecorderHandler::initialize(
     return false;
   }
   use_vp9_ = base::ToLowerASCII(codecs.utf8()).find("vp9") != std::string::npos;
-  media_stream_ = media_stream;
   DCHECK(client);
   client_ = client;
 
+  media_stream_ = media_stream;
+  DCHECK(MediaStream::GetMediaStream(media_stream));

[perkj_chrome, 2016/01/07 09:18:00]

no need for this check. The same will happen on the line below if
MediaStream::GetMediaStream return null.

[mcasas, 2016/01/08 00:14:12]

Done.

+  MediaStream::GetMediaStream(media_stream)->AddObserver(this);
+
   return true;
 }
 
@@ -202,6 +205,19 @@ void MediaRecorderHandler::resume() {
     video_recorder->Resume();
 }
 
+void MediaRecorderHandler::TrackAdded(const blink::WebMediaStreamTrack& track) {
+  WriteData(base::StringPiece(""));

[perkj_chrome, 2016/01/07 09:18:00]

Why is WriteData(base::StringPiece necessary here but not in the normal stop
condition? If it is required always, move to stop() ? 

[mcasas, 2016/01/08 00:14:12]

Actually both writeData() and stop() are not needed
since client->onError() (new name of fail...() ) will do
all necessary steps to stop the recording. Both 
removed.

+  stop();
+  client_->failIllegalStreamModification("Track added");
+}
+
+void MediaRecorderHandler::TrackRemoved(
+    const blink::WebMediaStreamTrack& track) {
+  WriteData(base::StringPiece(""));
+  stop();
+  client_->failIllegalStreamModification("Track removed");
+}
+
 void MediaRecorderHandler::OnEncodedVideo(
     const scoped_refptr<media::VideoFrame>& video_frame,
     scoped_ptr<std::string> encoded_data,