Add UMA metrics for ICE regathering reasons.

webrtc/p2p/base/dtlstransportchannel.h

 /*
  *  Copyright 2011 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 168 matching lines @@
     return channel_->gathering_state();
   }
 
   void AddRemoteCandidate(const Candidate& candidate) override {
     channel_->AddRemoteCandidate(candidate);
   }
   void RemoveRemoteCandidate(const Candidate& candidate) override {
     channel_->RemoveRemoteCandidate(candidate);
   }
 
+  void SetMetricsObserver(webrtc::MetricsObserverInterface* observer) override {
+    channel_->SetMetricsObserver(observer);
+  }
+
   void SetIceConfig(const IceConfig& config) override {
     channel_->SetIceConfig(config);
   }
 
   // Needed by DtlsTransport.
   TransportChannelImpl* channel() { return channel_; }
 
  private:
   void OnReadableState(TransportChannel* channel);
   void OnWritableState(TransportChannel* channel);
@@ skipping 39 matching lines @@
   // transport channel became writable, or before a remote fingerprint was
   // received.
   rtc::Buffer cached_client_hello_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(DtlsTransportChannelWrapper);
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_DTLSTRANSPORTCHANNEL_H_