Add 16-bit network id to the candidate signaling.

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 65f82e4f25fd28b11a7349fe14b84596b53cc9dd..4c5a15090e32b30efaefebc53281506c25ccd246 100644
--- a/webrtc/p2p/base/port.h
+++ b/webrtc/p2p/base/port.h
@@ -296,7 +296,7 @@ class Port : public PortInterface, public rtc::MessageHandler,
   void set_candidate_filter(uint32_t candidate_filter) {
     candidate_filter_ = candidate_filter;
   }
-  int32_t network_cost() const { return network_cost_; }
+  int16_t network_cost() const { return network_cost_; }
 
  protected:
   enum {
@@ -403,7 +403,7 @@ class Port : public PortInterface, public rtc::MessageHandler,
   // A virtual cost perceived by the user, usually based on the network type
   // (WiFi. vs. Cellular). It takes precedence over the priority when
   // comparing two connections.
-  uint32_t network_cost_;
+  uint16_t network_cost_;
 
   friend class Connection;
 };