Reland the CL to remove candidates when doing continual gathering

webrtc/p2p/base/faketransportcontroller.h

Index: webrtc/p2p/base/faketransportcontroller.h
diff --git a/webrtc/p2p/base/faketransportcontroller.h b/webrtc/p2p/base/faketransportcontroller.h
index c5e2afea54fdb4e747f5680f88e561547eef03dd..ae5e86669acdd9027a9e61acffa5e39ecba4bf85 100644
--- a/webrtc/p2p/base/faketransportcontroller.h
+++ b/webrtc/p2p/base/faketransportcontroller.h
@@ -216,6 +216,9 @@ class FakeTransportChannel : public TransportChannelImpl,
   void AddRemoteCandidate(const Candidate& candidate) override {
     remote_candidates_.push_back(candidate);
   }
+
+  void RemoveRemoteCandidate(const Candidate& candidate) override {}
+
   const Candidates& remote_candidates() const { return remote_candidates_; }
 
   void OnMessage(rtc::Message* msg) override {