Fix Chromium FYI bot breakage caused by ICE interface change

webrtc/p2p/base/mockicetransport.h

 /*
  *  Copyright 2016 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 39 matching lines @@
   const std::string& transport_name() const override { return transport_name_; }
   int component() const override { return 0; }
   void SetIceRole(IceRole role) override {}
   void SetIceTiebreaker(uint64_t tiebreaker) override {}
   // The ufrag and pwd in |ice_params| must be set
   // before candidate gathering can start.
   void SetIceParameters(const IceParameters& ice_params) override {}
   void SetRemoteIceParameters(const IceParameters& ice_params) override {}
   void SetRemoteIceMode(IceMode mode) override {}
   void SetIceConfig(const IceConfig& config) override {}
+  rtc::Optional<int> GetRttEstimate() override {
+    return rtc::Optional<int>();
+  }
   void MaybeStartGathering() override {}
   void SetMetricsObserver(webrtc::MetricsObserverInterface* observer) override {
   }
   void AddRemoteCandidate(const Candidate& candidate) override {}
   void RemoveRemoteCandidate(const Candidate& candidate) override {}
   IceGatheringState gathering_state() const override {
     return IceGatheringState::kIceGatheringComplete;
   }
 
   bool receiving() const override { return true; }
   bool writable() const override { return true; }
 
  private:
   std::string transport_name_;
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_MOCKICETRANSPORT_H_