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

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 7d5e304bb3318b6cd959e6b6445a0d801f71b462..25510c2f6418bb2cebe98d0dc86b7a3a486f8a9f 100644
--- a/webrtc/p2p/base/p2ptransportchannel.h
+++ b/webrtc/p2p/base/p2ptransportchannel.h
@@ -221,8 +221,8 @@ class P2PTransportChannel : public TransportChannelImpl,
   // 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