Implement browser-side logging to WebRtc log

content/browser/renderer_host/media/video_capture_controller.cc

Index: content/browser/renderer_host/media/video_capture_controller.cc
diff --git a/content/browser/renderer_host/media/video_capture_controller.cc b/content/browser/renderer_host/media/video_capture_controller.cc
index f23f50f82b2a771746ce012cbccebb0dc82cce94..602ee1ae4103e2c2ac9a6cffaf538e50efe58beb 100644
--- a/content/browser/renderer_host/media/video_capture_controller.cc
+++ b/content/browser/renderer_host/media/video_capture_controller.cc
@@ -121,7 +121,7 @@ class VideoCaptureController::VideoCaptureDeviceClient
                                         const gfx::Size& dimensions,
                                         base::TimeTicks timestamp,
                                         int frame_rate) OVERRIDE;
-  virtual void OnError() OVERRIDE;
+  virtual void OnError(const std::string& reason) OVERRIDE;
 
  private:
   scoped_refptr<Buffer> DoReserveOutputBuffer(media::VideoFrame::Format format,
@@ -428,7 +428,9 @@ void VideoCaptureController::VideoCaptureDeviceClient::OnIncomingCapturedBuffer(
           timestamp));
 }
 
-void VideoCaptureController::VideoCaptureDeviceClient::OnError() {
+void VideoCaptureController::VideoCaptureDeviceClient::OnError(
+    const std::string& reason) {
+  MediaStreamManager::AddLogMessage("Error on video capture: " + reason);

[perkj_chrome, 2014/01/22 10:03:29]

I think you should add an identifier - the session id in the call to
AddLogMessage. AddLogMessage can then find the request that contain devices with
that session id and only log to the render process that use the session id.

Note that a real device can be used in several tabs and thus have multiple
session ids. I am a bit lost of what VideoCaptureDeviceClient represents.

[vrk (LEFT CHROMIUM), 2014/01/22 18:30:30]

I'm not sure if it's worth doing this. Here's my reasoning: Look at how DVLOG is
used. There's nothing being done to disambiguate DVLOG messages between multiple
tabs/sessions, i.e. if there's an error for some camera X, it is logged to the
console without explaining which tab it came from. I don't think we need
anything more sophisticated than that for native logging.

[vrk (LEFT CHROMIUM), 2014/01/23 21:46:32]

Talked offline. I looked into this, and I don't think I can implement this
without making a lot of plumbing changes. Since I don't think we really need
this, I'm going to keep the CL as-is and fix in follow-up CL if need be.

   BrowserThread::PostTask(BrowserThread::IO,
       FROM_HERE,
       base::Bind(&VideoCaptureController::DoErrorOnIOThread, controller_));