Add UMA metrics for ICE regathering reasons.

webrtc/p2p/base/transportcontroller.cc

 /*
  *  Copyright 2015 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 169 matching lines @@
   auto it = FindChannel_n(transport_name, component);
   if (it != channels_.end()) {
     // Channel already exists; increment reference count and return.
     it->AddRef();
     return it->get();
   }
 
   // Need to create a new channel.
   Transport* transport = GetOrCreateTransport_n(transport_name);
   TransportChannelImpl* channel = transport->CreateChannel(component);
+  channel->SetMetricsObserver(metrics_observer_);
   channel->SignalWritableState.connect(
       this, &TransportController::OnChannelWritableState_n);
   channel->SignalReceivingState.connect(
       this, &TransportController::OnChannelReceivingState_n);
   channel->SignalGatheringState.connect(
       this, &TransportController::OnChannelGatheringState_n);
   channel->SignalCandidateGathered.connect(
       this, &TransportController::OnChannelCandidateGathered_n);
   channel->SignalCandidatesRemoved.connect(
       this, &TransportController::OnChannelCandidatesRemoved_n);
@@ skipping 497 matching lines @@
     signaling_thread_->Post(
         RTC_FROM_HERE, this, MSG_ICEGATHERINGSTATE,
         new rtc::TypedMessageData<IceGatheringState>(new_gathering_state));
   }
 }
 
 void TransportController::OnDtlsHandshakeError(rtc::SSLHandshakeError error) {
   SignalDtlsHandshakeError(error);
 }
 
+void TransportController::SetMetricsObserver(
+    webrtc::MetricsObserverInterface* metrics_observer) {
+  metrics_observer_ = metrics_observer;
+  for (auto channel : channels_) {
+    channel->SetMetricsObserver(metrics_observer);
+  }
+}
+
 }  // namespace cricket