Reland the CL to remove candidates when doing continual gathering

webrtc/p2p/base/p2ptransportchannel.h

Index: webrtc/p2p/base/p2ptransportchannel.h
diff --git a/webrtc/p2p/base/p2ptransportchannel.h b/webrtc/p2p/base/p2ptransportchannel.h
index 3ca25d4cba1425bd5a379c7c5f8b10e964e23e51..b86389a0bd5fa31b9c42c1e646addf2620b08e2c 100644
--- a/webrtc/p2p/base/p2ptransportchannel.h
+++ b/webrtc/p2p/base/p2ptransportchannel.h
@@ -92,6 +92,7 @@ class P2PTransportChannel : public TransportChannelImpl,
     return gathering_state_;
   }
   void AddRemoteCandidate(const Candidate& candidate) override;
+  void RemoveRemoteCandidate(const Candidate& candidate) override;
   // Sets the parameters in IceConfig. We do not set them blindly. Instead, we
   // only update the parameter if it is considered set in |config|. For example,
   // a negative value of receiving_timeout will be considered "not set" and we