Bug 1526039 - Fix protocol field in about:webrtc candidates table r=dminor

"transport" is the old name for the field.  This makes it so that the transport
protocol is no longer printed as "undefined" in the ICE candidate table.

Differential Revision: https://phabricator.services.mozilla.com/D39981

--HG--
extra : moz-landing-system : lando

toolkit/content/aboutwebrtc/aboutWebrtc.js

@@ -909,7 +909,7 @@ ICEStats.prototype = {
       type = `${c.candidateType}-${c.relayProtocol}`;
     }
 
-    return `${c.address}:${c.port}/${c.transport}(${type})`;
+    return `${c.address}:${c.port}/${c.protocol}(${type})`;
   },
 };