Implement browser-side logging to WebRtc log

content/browser/renderer_host/media/media_stream_manager.h

Index: content/browser/renderer_host/media/media_stream_manager.h
diff --git a/content/browser/renderer_host/media/media_stream_manager.h b/content/browser/renderer_host/media/media_stream_manager.h
index eefab6bdcb2087ddfc4890a8f7b1c93a3691050f..1f135ea95883a4bb6d58de872123bdfe26599554 100644
--- a/content/browser/renderer_host/media/media_stream_manager.h
+++ b/content/browser/renderer_host/media/media_stream_manager.h
@@ -67,6 +67,10 @@ class CONTENT_EXPORT MediaStreamManager
                               scoped_ptr<MediaStreamUIProxy> ui)>
       MediaRequestResponseCallback;
 
+  // Callback to log a message to native logs.
+  typedef base::Callback<void(const std::string& message)>
+      AddWebRtcLogCallback;
+
   explicit MediaStreamManager(media::AudioManager* audio_manager);
   virtual ~MediaStreamManager();
 
@@ -185,6 +189,10 @@ class CONTENT_EXPORT MediaStreamManager
   // too late. (see http://crbug.com/247525#c14).
   virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
 
+  // Adds |message| to native logs for outstanding device requests.

[Henrik Grunell, 2014/01/17 08:51:25]

Is sending the log to all outstanding requests' renderers what one would usually
want? I'm not particularly familiar with the MediaStream code in the browser
side, but it seems to me that we should log for the specific request this
message belongs to (if there is one, which I suppose there almost always is)?
Won't we spam logs with irrelevant information from other renderers this way?

[vrk (LEFT CHROMIUM), 2014/01/22 02:25:42]

See implementation of AddLogMessageOnUIThread(). This code should send all
outstanding requests to each respective RenderProcessHost, which will send it to
the respective WebRtcLogHandlerHost. 

So for example: 
render process id 1 has native logging started, calls getUserMedia
render process id 2 does not have native logging started, callsGetUserMedia

render process id 1 will send a log message to RenderProcessHost 1, which
forwards it to WebRtcLogHandlerHost, which will add the log because it has
started.
render process id 2 will send a log message to RenderProcessHost 2, which
forwards it to WebRtcLogHandlerHost, which will ignore the log message because
native logging never began.

Do you agree? Let me know if you still see an issue.

[Henrik Grunell, 2014/01/22 07:05:22]

Let's discuss offline.

+  void AddLogMessageOnUIThread(const std::string& message);
+  static void AddLogMessage(const std::string& message);
+
  protected:
   // Used for testing.
   MediaStreamManager();
@@ -285,6 +293,7 @@ class CONTENT_EXPORT MediaStreamManager
                                   const MediaStreamDevices& devices);
   void FinalizeEnumerateDevices(const std::string& label,
                                 DeviceRequest* request);
+  void DoAddLogMessage(const std::string& message);

[Henrik Grunell, 2014/01/17 08:51:25]

Remove. Not implemented as a member function.

[vrk (LEFT CHROMIUM), 2014/01/22 02:25:42]

Thanks, done.

 
   // This method is called when an audio or video device is plugged in or
   // removed. It make sure all MediaStreams that use a removed device is