Add network cost as part of the connection comparison.

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 436b1e7faafc2993f67e5905a35ef0e56f1f2cf2..95abe86464931e2d4029e0c5ac2c9770f998cc93 100644
--- a/webrtc/p2p/base/port.h
+++ b/webrtc/p2p/base/port.h
@@ -296,6 +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_; }
 
  protected:
   enum {
@@ -395,6 +396,11 @@ class Port : public PortInterface, public rtc::MessageHandler,
   // TurnPort will hide raddr to avoid local address leakage.
   uint32_t candidate_filter_;
 
+  // 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_;
+
   friend class Connection;
 };
 
@@ -560,6 +566,8 @@ class Connection : public rtc::MessageHandler,
 
   IceMode remote_ice_mode() const { return remote_ice_mode_; }
 
+  uint32_t ComputeNetworkCost() const;
+
   // Update the ICE password of the remote candidate if |ice_ufrag| matches
   // the candidate's ufrag, and the candidate's passwrod has not been set.
   void MaybeSetRemoteIceCredentials(const std::string& ice_ufrag,