Do not prune if the current best connection is weak.

webrtc/p2p/base/port.h

Index: webrtc/p2p/base/port.h
diff --git a/webrtc/p2p/base/port.h b/webrtc/p2p/base/port.h
index 8e7a2592d991661c59bc745e901d523c5b1dd9a8..47903be05b55753b063e6bc8630946d8938e59a1 100644
--- a/webrtc/p2p/base/port.h
+++ b/webrtc/p2p/base/port.h
@@ -436,6 +436,8 @@ class Connection : public rtc::MessageHandler,
   // be false for TCP connections.
   bool connected() const { return connected_; }
 
+  bool Weak() const { return !(writable() && receiving() && connected()); }
+
   // Estimate of the round-trip time over this connection.
   uint32 rtt() const { return rtt_; }