Start ICE connectivity checks as soon as the first pair is pingable.

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 f6021615f083e19ea0684355e7c884a4a56eaea9..5b32832b06ac1ac9c54ee965acedf2cf90c20561 100644
--- a/webrtc/p2p/base/p2ptransportchannel.h
+++ b/webrtc/p2p/base/p2ptransportchannel.h
@@ -93,7 +93,6 @@ class P2PTransportChannel : public TransportChannelImpl,
   void SetRemoteIceCredentials(const std::string& ice_ufrag,
                                const std::string& ice_pwd) override;
   void SetRemoteIceMode(IceMode mode) override;
-  void Connect() override;
   void MaybeStartGathering() override;
   IceGatheringState gathering_state() const override {
     return gathering_state_;
@@ -366,6 +365,7 @@ class P2PTransportChannel : public TransportChannelImpl,
   TransportChannelState state_ = TransportChannelState::STATE_INIT;
   IceConfig config_;
   int last_sent_packet_id_ = -1;  // -1 indicates no packet was sent before.
+  bool started_pinging_ = false;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(P2PTransportChannel);
 };