add url attribute to RTCIceCandidate

https://w3c.github.io/webrtc-stats/#dom-rtcicecandidatestats-url

aligning with how this is defined in webrtc-stats
and add deprecation note to the url attribute on the RTCIceEvent

webrtc.html

@@ -5926,6 +5926,7 @@ <h4>
   readonly attribute unsigned short? relatedPort;
   readonly attribute DOMString? usernameFragment;
   readonly attribute RTCIceServerTransportProtocol? relayProtocol;
+  readonly attribute DOMString? url;
   RTCIceCandidateInit toJSON();
 };</pre>
             <section>
@@ -6238,6 +6239,17 @@ <h2>
                     is only present for local relay candidates.
                   </p>
                 </dd>
+                <dt>
+                  <dfn>url</dfn> of type <span class=
+                  "idlMemberType">DOMString</span>
+                </dt>
+                <dd>
+                  <p>
+                    For local candidates of type {{RTCIceCandidateType/"srflx"}} or type
+                    {{RTCIceCandidateType/"relay"}} this is the URL of the ICE server
+                    from which the candidate was obtained.
+                  </p>
+                </dd>
               </dl>
             </section>
             <section>
@@ -6690,6 +6702,10 @@ <h2>
                     TURN server, this parameter will be set to
                     <code>null</code>.
                   </p>
+                  <p class="note">
+                    This attribute is deprecated; it exists for legacy compatibility reasons only.
+                    Prefer the candidate {{RTCIceCandidate/url}}.
+                  </p>
                 </dd>
               </dl>
             </section>