Do not switch a connection if the new connection is not ready to send packets.

webrtc/p2p/base/p2ptransportchannel.h

 /*
  *  Copyright 2004 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 203 matching lines @@
     remote_supports_renomination_ = remote_supports_renomination;
   }
 
  private:
   rtc::Thread* thread() const { return worker_thread_; }
   bool IsGettingPorts() { return allocator_session()->IsGettingPorts(); }
 
   // 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;
-  // Returns true if it's possible to send packets on this channel.
-  bool ReadyToSend() const;
+  // Returns true if it's possible to send packets on |connection|.
+  bool ReadyToSend(Connection* connection) const;
   void UpdateConnectionStates();
   void RequestSortAndStateUpdate();
   // Start pinging if we haven't already started, and we now have a connection
   // that's pingable.
   void MaybeStartPinging();
 
   // The methods below return a positive value if |a| is preferable to |b|,
   // a negative value if |b| is preferable, and 0 if they're equally preferable.
   // If |receiving_unchanged_threshold| is set, then when |b| is receiving and
   // |a| is not, returns a negative value only if |b| has been in receiving
@@ skipping 181 matching lines @@
   // The value put in the "nomination" attribute for the next nominated
   // connection. A zero-value indicates the connection will not be nominated.
   uint32_t nomination_ = 0;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(P2PTransportChannel);
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_P2PTRANSPORTCHANNEL_H_