Make RTC work on Firefox (mostly).

tools/dom/templates/html/impl/impl_RTCPeerConnection.darttemplate

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of $LIBRARYNAME;
 
 $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 $if DART2JS
   factory $CLASSNAME(Map rtcIceServers, [Map mediaConstraints]) {
     var constructorName = JS('RtcPeerConnection', 'window[#]',
@@ skipping 11 matching lines @@
 
   /**
    * Checks if Real Time Communication (RTC) APIs are supported and enabled on
    * the current platform.
    */
 $if DART2JS
   static bool get supported {
     // Currently in Firefox some of the RTC elements are defined but throw an
     // error unless the user has specifically enabled them in their
     // about:config. So we have to construct an element to actually test if RTC
-    // is supported at at the given time.
+    // is supported at the given time. 
     try {
-      var c = new RtcPeerConnection({"iceServers": [ {"url":"stun:foo.com"}]});
-      return c is RtcPeerConnection;
-    } catch (_) {}
+      new RtcPeerConnection(
+          {"iceServers": [ {"url":"stun:localhost"}]});
+      return true;
+    } catch (_) { return false;}
     return false;
   }
 $else
   static bool get supported => true;
 $endif
   Future<RtcSessionDescription> createOffer([Map mediaConstraints]) {
     var completer = new Completer<RtcSessionDescription>();
     _createOffer(
         (value) { completer.complete(value); },
         (error) { completer.completeError(error); }, mediaConstraints);
     return completer.future;
   }
 
   Future<RtcSessionDescription> createAnswer([Map mediaConstraints]) {
     var completer = new Completer<RtcSessionDescription>();
     _createAnswer(
         (value) { completer.complete(value); },
         (error) { completer.completeError(error); }, mediaConstraints);
     return completer.future;
   }
 $!MEMBERS
 }
-
-