Stop a session when a new connection becomes writable.

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 51979df8d8e1fe8a277368ea0684f36dbbb89d6b..73036310d66d23e92c9a7f5077466aec78238dc8 100644
--- a/webrtc/p2p/base/p2ptransportchannel.h
+++ b/webrtc/p2p/base/p2ptransportchannel.h
@@ -156,12 +156,15 @@ class P2PTransportChannel : public TransportChannelImpl,
   // Public for unit tests.
   Connection* FindNextPingableConnection();
 
- private:
-  rtc::Thread* thread() { return worker_thread_; }
+  // Helper method used only in unit tests.
   PortAllocatorSession* allocator_session() {
     return allocator_sessions_.back();
   }
 
+ private:
+  rtc::Thread* thread() { return worker_thread_; }
+
+
   // A transport channel is weak if the current best connection is either
   // not receiving or not writable, or if there is no best connection at all.
   bool weak() const;
@@ -173,6 +176,7 @@ class P2PTransportChannel : public TransportChannelImpl,
   void HandleWritable();
   void HandleNotWritable();
   void HandleAllTimedOut();
+  void MaybeStopSessions();
 
   Connection* GetBestConnectionOnNetwork(rtc::Network* network) const;
   bool CreateConnections(const Candidate& remote_candidate,
@@ -234,7 +238,6 @@ class P2PTransportChannel : public TransportChannelImpl,
   Connection* pending_best_connection_;
   std::vector<RemoteCandidate> remote_candidates_;
   bool sort_dirty_;  // indicates whether another sort is needed right now
-  bool was_writable_;
   bool had_connection_ = false;  // if connections_ has ever been nonempty
   typedef std::map<rtc::Socket::Option, int> OptionMap;
   OptionMap options_;
@@ -252,6 +255,9 @@ class P2PTransportChannel : public TransportChannelImpl,
   int receiving_timeout_;
   uint32_t last_ping_sent_ms_ = 0;
   bool gather_continually_ = false;
+  // Whether a new session has been started to get ports and it is not
+  // stopped yet.
+  bool is_getting_ports_  = false;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(P2PTransportChannel);
 };