Ping backup connection at a slower rate

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 62ca3a50b78b80dab18babc2d2bd038ad9d3c44a..1e79172af7947ba7f2292eb8c8a3f1a5bb2d2302 100644
--- a/webrtc/p2p/base/port.h
+++ b/webrtc/p2p/base/port.h
@@ -522,6 +522,9 @@ class Connection : public rtc::MessageHandler,
   uint32_t last_ping_sent() const { return last_ping_sent_; }
   void Ping(uint32_t now);
   void ReceivedPingResponse();
+  uint32_t last_ping_response_received() const {
+    return last_ping_response_received_;
+  }
 
   // Called whenever a valid ping is received on this connection.  This is
   // public because the connection intercepts the first ping for us.