The Tor Browser / file revision

 /* -*- Mode: Javascript; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* vim: set ft=javascript ts=2 et sw=2 tw=80: */

 /* 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/. */

 const {Cc, Ci, Cu, Cr} = require("chrome");

 Cu.import("resource://gre/modules/Services.jsm");

 Cu.import("resource://gre/modules/devtools/event-emitter.js");

 exports.PREF_ORIG_SOURCES = "devtools.styleeditor.source-maps-enabled";

 /**

  * A PreferenceObserver observes a pref branch for pref changes.

  * It emits an event for each preference change.

  */

 function PrefObserver(branchName) {

   this.branchName = branchName;

   this.branch = Services.prefs.getBranch(branchName);

   this.branch.addObserver("", this, false);

   EventEmitter.decorate(this);

 }

 exports.PrefObserver = PrefObserver;

 PrefObserver.prototype = {

   observe: function(subject, topic, data) {

     if (topic == "nsPref:changed") {

       this.emit(this.branchName + data);

     }

   },

   destroy: function() {

     if (this.branch) {

       this.branch.removeObserver('', this);

     }

   }

 };