Add the URL attribute to cricket::Candiate. (Objc wrapper)

webrtc/api/jsepicecandidate.h

Index: webrtc/api/jsepicecandidate.h
diff --git a/webrtc/api/jsepicecandidate.h b/webrtc/api/jsepicecandidate.h
index f06863765c911b81d3c0b76708750a598706e59d..a8919e0a00e3254ead036e5c0809b03475eefa8a 100644
--- a/webrtc/api/jsepicecandidate.h
+++ b/webrtc/api/jsepicecandidate.h
@@ -43,6 +43,8 @@ class JsepIceCandidate : public IceCandidateInterface {
     return candidate_;
   }
 
+  virtual std::string server_url() const { return candidate_.url(); }
+
   virtual bool ToString(std::string* out) const;
 
  private: