The Tor Browser / file revision

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 function referencesVia(from, edge, to) {

     if (typeof findReferences !== 'function')

         return true;

     edge = "edge: " + edge;

     var edges = findReferences(to);

     if (edge in edges && edges[edge].indexOf(from) != -1)

         return true;

     // Be nice: make it easy to fix if the edge name has just changed.

     var alternatives = [];

     for (var e in edges) {

         if (edges[e].indexOf(from) != -1)

             alternatives.push(e);

     }

     if (alternatives.length == 0) {

         print("referent not referred to by referrer after all");

     } else {

         print("referent is not referenced via: " + uneval(edge));

         print("but it is referenced via:       " + uneval(alternatives));

     }

     print("all incoming edges, from any object:");

     for (var e in edges)

         print(e);

     return false;

 }