Late initialize MediaController, for less resource i.e. ProcessThread, usage by PeerConnection.

webrtc/api/statscollector.cc

 /*
  *  Copyright 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 444 matching lines @@
   double time_now = GetTimeNow();
   // Calls to UpdateStats() that occur less than kMinGatherStatsPeriod number of
   // ms apart will be ignored.
   const double kMinGatherStatsPeriod = 50;
   if (stats_gathering_started_ != 0 &&
       stats_gathering_started_ + kMinGatherStatsPeriod > time_now) {
     return;
   }
   stats_gathering_started_ = time_now;
 
+  // TODO(pthatcher): Merge PeerConnection and WebRtcSession so there is no
+  // pc_->session().
   if (pc_->session()) {
     // TODO(tommi): All of these hop over to the worker thread to fetch
     // information.  We could use an AsyncInvoker to run all of these and post
     // the information back to the signaling thread where we can create and
     // update stats reports.  That would also clean up the threading story a bit
     // since we'd be creating/updating the stats report objects consistently on
     // the same thread (this class has no locks right now).
     ExtractSessionInfo();
     ExtractVoiceInfo();
     ExtractVideoInfo(level);
@@ skipping 461 matching lines @@
     StatsReport* report = entry.second;
     report->set_timestamp(stats_gathering_started_);
   }
 }
 
 void StatsCollector::ClearUpdateStatsCacheForTest() {
   stats_gathering_started_ = 0;
 }
 
 }  // namespace webrtc