Adding more detail to MessageQueue::Dispatch logging.

talk/app/webrtc/objc/avfoundationvideocapturer.mm

 /*
  * libjingle
  * Copyright 2015 Google Inc.
  *
  * 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 notice,
@@ skipping 469 matching lines @@
 
   CVImageBufferRef image_buffer = CMSampleBufferGetImageBuffer(sampleBuffer);
   if (image_buffer == NULL) {
     return;
   }
 
   // Retain the buffer and post it to the webrtc thread. It will be released
   // after it has successfully been signaled.
   CVBufferRetain(image_buffer);
   AVFoundationFrame frame(image_buffer, rtc::TimeNanos());
-  _startThread->Post(this, kMessageTypeFrame,
+  _startThread->Post(RTC_FROM_HERE, this, kMessageTypeFrame,
                      new rtc::TypedMessageData<AVFoundationFrame>(frame));
 }
 
 void AVFoundationVideoCapturer::OnMessage(rtc::Message *msg) {
   switch (msg->message_id) {
     case kMessageTypeFrame: {
       rtc::TypedMessageData<AVFoundationFrame>* data =
         static_cast<rtc::TypedMessageData<AVFoundationFrame>*>(msg->pdata);
       const AVFoundationFrame& frame = data->data();
       OnFrameMessage(frame.image_buffer, frame.capture_time);
@@ skipping 52 matching lines @@
 
   // This will call a superclass method that will perform the frame conversion
   // to I420.
   SignalFrameCaptured(this, &frame);
 
   CVPixelBufferUnlockBaseAddress(image_buffer, lock_flags);
   CVBufferRelease(image_buffer);
 }
 
 }  // namespace webrtc