Start ICE connectivity checks as soon as the first pair is pingable.

webrtc/p2p/base/port.cc

Index: webrtc/p2p/base/port.cc
diff --git a/webrtc/p2p/base/port.cc b/webrtc/p2p/base/port.cc
index ab7ba09ea513a61a8876a4ad47999a1a6aa57d11..1a40033e3b517e9c4c80b89d6a822ee8c739b81c 100644
--- a/webrtc/p2p/base/port.cc
+++ b/webrtc/p2p/base/port.cc
@@ -1233,7 +1233,7 @@ bool Connection::dead(int64_t now) const {
   return now > (time_created_ms_ + MIN_CONNECTION_LIFETIME);
 }
 
-bool Connection::stable(int64_t now) {
+bool Connection::stable(int64_t now) const {
   // A connection is stable if it's RTT has converged and it isn't missing any
   // responses.  We should send pings at a higher rate until the RTT converges
   // and whenever a ping response is missing (so that we can detect
@@ -1505,11 +1505,11 @@ void Connection::MaybeAddPrflxCandidate(ConnectionRequest* request,
   SignalStateChange(this);
 }
 
-bool Connection::rtt_converged() {
+bool Connection::rtt_converged() const {
   return rtt_samples_ > (RTT_RATIO + 1);
 }
 
-bool Connection::missing_responses(int64_t now) {
+bool Connection::missing_responses(int64_t now) const {
   if (pings_since_last_response_.empty()) {
     return false;
   }