The Tor Browser / file revision

 "use strict";

 const Cc = Components.classes;

 const Ci = Components.interfaces;

 const Cu = Components.utils;

 const Cr = Components.results;

 const { devtools } = Cu.import("resource://gre/modules/devtools/Loader.jsm", {});

 const { require } = devtools;

 this.sourceMap = require("source-map");

 this.acorn = require("acorn/acorn");

 this.prettyFast = require("devtools/pretty-fast");

 const { console } = Cu.import("resource://gre/modules/devtools/Console.jsm", {});

 // Register a console listener, so console messages don't just disappear

 // into the ether.

 let errorCount = 0;

 let listener = {

   observe: function (aMessage) {

     errorCount++;

     try {

       // If we've been given an nsIScriptError, then we can print out

       // something nicely formatted, for tools like Emacs to pick up.

       var scriptError = aMessage.QueryInterface(Ci.nsIScriptError);

       dump(aMessage.sourceName + ":" + aMessage.lineNumber + ": " +

            scriptErrorFlagsToKind(aMessage.flags) + ": " +

            aMessage.errorMessage + "\n");

       var string = aMessage.errorMessage;

     } catch (x) {

       // Be a little paranoid with message, as the whole goal here is to lose

       // no information.

       try {

         var string = "" + aMessage.message;

       } catch (x) {

         var string = "<error converting error message to string>";

       }

     }

     do_throw("head_pretty-fast.js got console message: " + string + "\n");

   }

 };

 let consoleService = Cc["@mozilla.org/consoleservice;1"].getService(Ci.nsIConsoleService);

 consoleService.registerListener(listener);