The Tor Browser: toolkit/mozapps/extensions/LightweightThemeManager.jsm@6474c204b198 (annotated)

toolkit/mozapps/extensions/LightweightThemeManager.jsm@6474c204b198 (annotated)

toolkit/mozapps/extensions/LightweightThemeManager.jsm

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* 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/. */
 "use strict";
 this.EXPORTED_SYMBOLS = ["LightweightThemeManager"];
 const Cc = Components.classes;
 const Ci = Components.interfaces;
 Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
 Components.utils.import("resource://gre/modules/AddonManager.jsm");
 Components.utils.import("resource://gre/modules/Services.jsm");
 const ID_SUFFIX              = "@personas.mozilla.org";
 const PREF_LWTHEME_TO_SELECT = "extensions.lwThemeToSelect";
 const PREF_GENERAL_SKINS_SELECTEDSKIN = "general.skins.selectedSkin";
 const PREF_EM_DSS_ENABLED    = "extensions.dss.enabled";
 const ADDON_TYPE             = "theme";
 const URI_EXTENSION_STRINGS  = "chrome://mozapps/locale/extensions/extensions.properties";
 const STRING_TYPE_NAME       = "type.%ID%.name";
 const DEFAULT_MAX_USED_THEMES_COUNT = 30;
 const MAX_PREVIEW_SECONDS = 30;
 const MANDATORY = ["id", "name", "headerURL"];
 const OPTIONAL = ["footerURL", "textcolor", "accentcolor", "iconURL",
                   "previewURL", "author", "description", "homepageURL",
                   "updateURL", "version"];
 const PERSIST_ENABLED = true;
 const PERSIST_BYPASS_CACHE = false;
 const PERSIST_FILES = {
   headerURL: "lightweighttheme-header",
   footerURL: "lightweighttheme-footer"
 };
 XPCOMUtils.defineLazyModuleGetter(this, "LightweightThemeImageOptimizer",
   "resource://gre/modules/addons/LightweightThemeImageOptimizer.jsm");
 this.__defineGetter__("_prefs", function prefsGetter() {
   delete this._prefs;
   return this._prefs = Services.prefs.getBranch("lightweightThemes.");
 });
 this.__defineGetter__("_maxUsedThemes", function maxUsedThemesGetter() {
   delete this._maxUsedThemes;
   try {
     this._maxUsedThemes = _prefs.getIntPref("maxUsedThemes");
   }
   catch (e) {
     this._maxUsedThemes = DEFAULT_MAX_USED_THEMES_COUNT;
   }
   return this._maxUsedThemes;
 });
 this.__defineSetter__("_maxUsedThemes", function maxUsedThemesSetter(aVal) {
   delete this._maxUsedThemes;
   return this._maxUsedThemes = aVal;
 });
 // Holds the ID of the theme being enabled or disabled while sending out the
 // events so cached AddonWrapper instances can return correct values for
 // permissions and pendingOperations
 var _themeIDBeingEnabled = null;
 var _themeIDBeingDisabled = null;
 this.LightweightThemeManager = {
   get usedThemes () {
     try {
       return JSON.parse(_prefs.getComplexValue("usedThemes",
                                                Ci.nsISupportsString).data);
     } catch (e) {
       return [];
     }
   },
   get currentTheme () {
     try {
       if (_prefs.getBoolPref("isThemeSelected"))
         var data = this.usedThemes[0];
     } catch (e) {}
     return data || null;
   },
   get currentThemeForDisplay () {
     var data = this.currentTheme;
     if (data && PERSIST_ENABLED) {
       for (let key in PERSIST_FILES) {
         try {
           if (data[key] && _prefs.getBoolPref("persisted." + key))
             data[key] = _getLocalImageURI(PERSIST_FILES[key]).spec
                         + "?" + data.id + ";" + _version(data);
         } catch (e) {}
       }
     }
     return data;
   },
   set currentTheme (aData) {
     return _setCurrentTheme(aData, false);
   },
   setLocalTheme: function LightweightThemeManager_setLocalTheme(aData) {
     _setCurrentTheme(aData, true);
   },
   getUsedTheme: function LightweightThemeManager_getUsedTheme(aId) {
     var usedThemes = this.usedThemes;
     for (let usedTheme of usedThemes) {
       if (usedTheme.id == aId)
         return usedTheme;
     }
     return null;
   },
   forgetUsedTheme: function LightweightThemeManager_forgetUsedTheme(aId) {
     let theme = this.getUsedTheme(aId);
     if (!theme)
       return;
     let wrapper = new AddonWrapper(theme);
     AddonManagerPrivate.callAddonListeners("onUninstalling", wrapper, false);
     var currentTheme = this.currentTheme;
     if (currentTheme && currentTheme.id == aId) {
       this.themeChanged(null);
       AddonManagerPrivate.notifyAddonChanged(null, ADDON_TYPE, false);
     }
     _updateUsedThemes(_usedThemesExceptId(aId));
     AddonManagerPrivate.callAddonListeners("onUninstalled", wrapper);
   },
   previewTheme: function LightweightThemeManager_previewTheme(aData) {
     if (!aData)
       return;
     let cancel = Cc["@mozilla.org/supports-PRBool;1"].createInstance(Ci.nsISupportsPRBool);
     cancel.data = false;
     Services.obs.notifyObservers(cancel, "lightweight-theme-preview-requested",
                                  JSON.stringify(aData));
     if (cancel.data)
       return;
     if (_previewTimer)
       _previewTimer.cancel();
     else
       _previewTimer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
     _previewTimer.initWithCallback(_previewTimerCallback,
                                    MAX_PREVIEW_SECONDS * 1000,
                                    _previewTimer.TYPE_ONE_SHOT);
     _notifyWindows(aData);
   },
   resetPreview: function LightweightThemeManager_resetPreview() {
     if (_previewTimer) {
       _previewTimer.cancel();
       _previewTimer = null;
       _notifyWindows(this.currentThemeForDisplay);
     }
   },
   parseTheme: function LightweightThemeManager_parseTheme(aString, aBaseURI) {
     try {
       return _sanitizeTheme(JSON.parse(aString), aBaseURI, false);
     } catch (e) {
       return null;
     }
   },
   updateCurrentTheme: function LightweightThemeManager_updateCurrentTheme() {
     try {
       if (!_prefs.getBoolPref("update.enabled"))
         return;
     } catch (e) {
       return;
     }
     var theme = this.currentTheme;
     if (!theme || !theme.updateURL)
       return;
     var req = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"]
                 .createInstance(Ci.nsIXMLHttpRequest);
     req.mozBackgroundRequest = true;
     req.overrideMimeType("text/plain");
     req.open("GET", theme.updateURL, true);
     // Prevent the request from reading from the cache.
     req.channel.loadFlags |= Ci.nsIRequest.LOAD_BYPASS_CACHE;
     // Prevent the request from writing to the cache.
     req.channel.loadFlags |= Ci.nsIRequest.INHIBIT_CACHING;
     var self = this;
     req.addEventListener("load", function loadEventListener() {
       if (req.status != 200)
         return;
       let newData = self.parseTheme(req.responseText, theme.updateURL);
       if (!newData ||
           newData.id != theme.id ||
           _version(newData) == _version(theme))
         return;
       var currentTheme = self.currentTheme;
       if (currentTheme && currentTheme.id == theme.id)
         self.currentTheme = newData;
     }, false);
     req.send(null);
   },
   /**
    * Switches to a new lightweight theme.
    *
    * @param  aData
    *         The lightweight theme to switch to
    */
   themeChanged: function LightweightThemeManager_themeChanged(aData) {
     if (_previewTimer) {
       _previewTimer.cancel();
       _previewTimer = null;
     }
     if (aData) {
       let usedThemes = _usedThemesExceptId(aData.id);
       usedThemes.unshift(aData);
       _updateUsedThemes(usedThemes);
       if (PERSIST_ENABLED) {
         LightweightThemeImageOptimizer.purge();
         _persistImages(aData, function themeChanged_persistImages() {
           _notifyWindows(this.currentThemeForDisplay);
         }.bind(this));
       }
     }
     _prefs.setBoolPref("isThemeSelected", aData != null);
     _notifyWindows(aData);
     Services.obs.notifyObservers(null, "lightweight-theme-changed", null);
   },
   /**
    * Starts the Addons provider and enables the new lightweight theme if
    * necessary.
    */
   startup: function LightweightThemeManager_startup() {
     if (Services.prefs.prefHasUserValue(PREF_LWTHEME_TO_SELECT)) {
       let id = Services.prefs.getCharPref(PREF_LWTHEME_TO_SELECT);
       if (id)
         this.themeChanged(this.getUsedTheme(id));
       else
         this.themeChanged(null);
       Services.prefs.clearUserPref(PREF_LWTHEME_TO_SELECT);
     }
     _prefs.addObserver("", _prefObserver, false);
   },
   /**
    * Shuts down the provider.
    */
   shutdown: function LightweightThemeManager_shutdown() {
     _prefs.removeObserver("", _prefObserver);
   },
   /**
    * Called when a new add-on has been enabled when only one add-on of that type
    * can be enabled.
    *
    * @param  aId
    *         The ID of the newly enabled add-on
    * @param  aType
    *         The type of the newly enabled add-on
    * @param  aPendingRestart
    *         true if the newly enabled add-on will only become enabled after a
    *         restart
    */
   addonChanged: function LightweightThemeManager_addonChanged(aId, aType, aPendingRestart) {
     if (aType != ADDON_TYPE)
       return;
     let id = _getInternalID(aId);
     let current = this.currentTheme;
     try {
       let next = Services.prefs.getCharPref(PREF_LWTHEME_TO_SELECT);
       if (id == next && aPendingRestart)
         return;
       Services.prefs.clearUserPref(PREF_LWTHEME_TO_SELECT);
       if (next) {
         AddonManagerPrivate.callAddonListeners("onOperationCancelled",
                                                new AddonWrapper(this.getUsedTheme(next)));
       }
       else {
         if (id == current.id) {
           AddonManagerPrivate.callAddonListeners("onOperationCancelled",
                                                  new AddonWrapper(current));
           return;
         }
       }
     }
     catch (e) {
     }
     if (current) {
       if (current.id == id)
         return;
       _themeIDBeingDisabled = current.id;
       let wrapper = new AddonWrapper(current);
       if (aPendingRestart) {
         Services.prefs.setCharPref(PREF_LWTHEME_TO_SELECT, "");
         AddonManagerPrivate.callAddonListeners("onDisabling", wrapper, true);
       }
       else {
         AddonManagerPrivate.callAddonListeners("onDisabling", wrapper, false);
         this.themeChanged(null);
         AddonManagerPrivate.callAddonListeners("onDisabled", wrapper);
       }
       _themeIDBeingDisabled = null;
     }
     if (id) {
       let theme = this.getUsedTheme(id);
       _themeIDBeingEnabled = id;
       let wrapper = new AddonWrapper(theme);
       if (aPendingRestart) {
         AddonManagerPrivate.callAddonListeners("onEnabling", wrapper, true);
         Services.prefs.setCharPref(PREF_LWTHEME_TO_SELECT, id);
         // Flush the preferences to disk so they survive any crash
         Services.prefs.savePrefFile(null);
       }
       else {
         AddonManagerPrivate.callAddonListeners("onEnabling", wrapper, false);
         this.themeChanged(theme);
         AddonManagerPrivate.callAddonListeners("onEnabled", wrapper);
       }
       _themeIDBeingEnabled = null;
     }
   },
   /**
    * Called to get an Addon with a particular ID.
    *
    * @param  aId
    *         The ID of the add-on to retrieve
    * @param  aCallback
    *         A callback to pass the Addon to
    */
   getAddonByID: function LightweightThemeManager_getAddonByID(aId, aCallback) {
     let id = _getInternalID(aId);
     if (!id) {
       aCallback(null);
       return;
      }
     let theme = this.getUsedTheme(id);
     if (!theme) {
       aCallback(null);
       return;
     }
     aCallback(new AddonWrapper(theme));
   },
   /**
    * Called to get Addons of a particular type.
    *
    * @param  aTypes
    *         An array of types to fetch. Can be null to get all types.
    * @param  aCallback
    *         A callback to pass an array of Addons to
    */
   getAddonsByTypes: function LightweightThemeManager_getAddonsByTypes(aTypes, aCallback) {
     if (aTypes && aTypes.indexOf(ADDON_TYPE) == -1) {
       aCallback([]);
       return;
     }
     aCallback([new AddonWrapper(a) for each (a in this.usedThemes)]);
   },
 };
 /**
  * The AddonWrapper wraps lightweight theme to provide the data visible to
  * consumers of the AddonManager API.
  */
 function AddonWrapper(aTheme) {
   this.__defineGetter__("id", function AddonWrapper_idGetter() aTheme.id + ID_SUFFIX);
   this.__defineGetter__("type", function AddonWrapper_typeGetter() ADDON_TYPE);
   this.__defineGetter__("isActive", function AddonWrapper_isActiveGetter() {
     let current = LightweightThemeManager.currentTheme;
     if (current)
       return aTheme.id == current.id;
     return false;
   });
   this.__defineGetter__("name", function AddonWrapper_nameGetter() aTheme.name);
   this.__defineGetter__("version", function AddonWrapper_versionGetter() {
     return "version" in aTheme ? aTheme.version : "";
   });
   ["description", "homepageURL", "iconURL"].forEach(function(prop) {
     this.__defineGetter__(prop, function AddonWrapper_optionalPropGetter() {
       return prop in aTheme ? aTheme[prop] : null;
     });
   }, this);
   ["installDate", "updateDate"].forEach(function(prop) {
     this.__defineGetter__(prop, function AddonWrapper_datePropGetter() {
       return prop in aTheme ? new Date(aTheme[prop]) : null;
     });
   }, this);
   this.__defineGetter__("creator", function AddonWrapper_creatorGetter() {
     return new AddonManagerPrivate.AddonAuthor(aTheme.author);
   });
   this.__defineGetter__("screenshots", function AddonWrapper_screenshotsGetter() {
     let url = aTheme.previewURL;
     return [new AddonManagerPrivate.AddonScreenshot(url)];
   });
   this.__defineGetter__("pendingOperations",
                        function AddonWrapper_pendingOperationsGetter() {
     let pending = AddonManager.PENDING_NONE;
     if (this.isActive == this.userDisabled)
       pending |= this.isActive ? AddonManager.PENDING_DISABLE : AddonManager.PENDING_ENABLE;
     return pending;
   });
   this.__defineGetter__("operationsRequiringRestart",
                function AddonWrapper_operationsRequiringRestartGetter() {
     // If a non-default theme is in use then a restart will be required to
     // enable lightweight themes unless dynamic theme switching is enabled
     if (Services.prefs.prefHasUserValue(PREF_GENERAL_SKINS_SELECTEDSKIN)) {
       try {
         if (Services.prefs.getBoolPref(PREF_EM_DSS_ENABLED))
           return AddonManager.OP_NEEDS_RESTART_NONE;
       }
       catch (e) {
       }
       return AddonManager.OP_NEEDS_RESTART_ENABLE;
     }
     return AddonManager.OP_NEEDS_RESTART_NONE;
   });
   this.__defineGetter__("size", function AddonWrapper_sizeGetter() {
     // The size changes depending on whether the theme is in use or not, this is
     // probably not worth exposing.
     return null;
   });
   this.__defineGetter__("permissions", function AddonWrapper_permissionsGetter() {
     let permissions = AddonManager.PERM_CAN_UNINSTALL;
     if (this.userDisabled)
       permissions |= AddonManager.PERM_CAN_ENABLE;
     else
       permissions |= AddonManager.PERM_CAN_DISABLE;
     return permissions;
   });
   this.__defineGetter__("userDisabled", function AddonWrapper_userDisabledGetter() {
     if (_themeIDBeingEnabled == aTheme.id)
       return false;
     if (_themeIDBeingDisabled == aTheme.id)
       return true;
     try {
       let toSelect = Services.prefs.getCharPref(PREF_LWTHEME_TO_SELECT);
       return aTheme.id != toSelect;
     }
     catch (e) {
       let current = LightweightThemeManager.currentTheme;
       return !current || current.id != aTheme.id;
     }
   });
   this.__defineSetter__("userDisabled", function AddonWrapper_userDisabledSetter(val) {
     if (val == this.userDisabled)
       return val;
     if (val)
       LightweightThemeManager.currentTheme = null;
     else
       LightweightThemeManager.currentTheme = aTheme;
     return val;
   });
   this.uninstall = function AddonWrapper_uninstall() {
     LightweightThemeManager.forgetUsedTheme(aTheme.id);
   };
   this.cancelUninstall = function AddonWrapper_cancelUninstall() {
     throw new Error("Theme is not marked to be uninstalled");
   };
   this.findUpdates = function AddonWrapper_findUpdates(listener, reason, appVersion, platformVersion) {
     AddonManagerPrivate.callNoUpdateListeners(this, listener, reason, appVersion, platformVersion);
   };
 }
 AddonWrapper.prototype = {
   // Lightweight themes are never disabled by the application
   get appDisabled() {
     return false;
   },
   // Lightweight themes are always compatible
   get isCompatible() {
     return true;
   },
   get isPlatformCompatible() {
     return true;
   },
   get scope() {
     return AddonManager.SCOPE_PROFILE;
   },
   get foreignInstall() {
     return false;
   },
   // Lightweight themes are always compatible
   isCompatibleWith: function AddonWrapper_isCompatibleWith(appVersion, platformVersion) {
     return true;
   },
   // Lightweight themes are always securely updated
   get providesUpdatesSecurely() {
     return true;
   },
   // Lightweight themes are never blocklisted
   get blocklistState() {
     return Ci.nsIBlocklistService.STATE_NOT_BLOCKED;
   }
 };
 /**
  * Converts the ID used by the public AddonManager API to an lightweight theme
  * ID.
  *
  * @param   id
  *          The ID to be converted
  *
  * @return  the lightweight theme ID or null if the ID was not for a lightweight
  *          theme.
  */
 function _getInternalID(id) {
   if (!id)
     return null;
   let len = id.length - ID_SUFFIX.length;
   if (len > 0 && id.substring(len) == ID_SUFFIX)
     return id.substring(0, len);
   return null;
 }
 function _setCurrentTheme(aData, aLocal) {
   aData = _sanitizeTheme(aData, null, aLocal);
   let needsRestart = (ADDON_TYPE == "theme") &&
                      Services.prefs.prefHasUserValue(PREF_GENERAL_SKINS_SELECTEDSKIN);
   let cancel = Cc["@mozilla.org/supports-PRBool;1"].createInstance(Ci.nsISupportsPRBool);
   cancel.data = false;
   Services.obs.notifyObservers(cancel, "lightweight-theme-change-requested",
                                JSON.stringify(aData));
   if (aData) {
     let theme = LightweightThemeManager.getUsedTheme(aData.id);
     let isInstall = !theme || theme.version != aData.version;
     if (isInstall) {
       aData.updateDate = Date.now();
       if (theme && "installDate" in theme)
         aData.installDate = theme.installDate;
       else
         aData.installDate = aData.updateDate;
       var oldWrapper = theme ? new AddonWrapper(theme) : null;
       var wrapper = new AddonWrapper(aData);
       AddonManagerPrivate.callInstallListeners("onExternalInstall", null,
                                                wrapper, oldWrapper, false);
       AddonManagerPrivate.callAddonListeners("onInstalling", wrapper, false);
     }
     let current = LightweightThemeManager.currentTheme;
     let usedThemes = _usedThemesExceptId(aData.id);
     if (current && current.id != aData.id)
       usedThemes.splice(1, 0, aData);
     else
       usedThemes.unshift(aData);
     _updateUsedThemes(usedThemes);
     if (isInstall)
        AddonManagerPrivate.callAddonListeners("onInstalled", wrapper);
   }
   if (cancel.data)
     return null;
   AddonManagerPrivate.notifyAddonChanged(aData ? aData.id + ID_SUFFIX : null,
                                          ADDON_TYPE, needsRestart);
   return LightweightThemeManager.currentTheme;
 }
 function _sanitizeTheme(aData, aBaseURI, aLocal) {
   if (!aData || typeof aData != "object")
     return null;
   var resourceProtocols = ["http", "https"];
   if (aLocal)
     resourceProtocols.push("file");
   var resourceProtocolExp = new RegExp("^(" + resourceProtocols.join("|") + "):");
   function sanitizeProperty(prop) {
     if (!(prop in aData))
       return null;
     if (typeof aData[prop] != "string")
       return null;
     let val = aData[prop].trim();
     if (!val)
       return null;
     if (!/URL$/.test(prop))
       return val;
     try {
       val = _makeURI(val, aBaseURI ? _makeURI(aBaseURI) : null).spec;
       if ((prop == "updateURL" ? /^https:/ : resourceProtocolExp).test(val))
         return val;
       return null;
     }
     catch (e) {
       return null;
     }
   }
   let result = {};
   for (let mandatoryProperty of MANDATORY) {
     let val = sanitizeProperty(mandatoryProperty);
     if (!val)
       throw Components.results.NS_ERROR_INVALID_ARG;
     result[mandatoryProperty] = val;
   }
   for (let optionalProperty of OPTIONAL) {
     let val = sanitizeProperty(optionalProperty);
     if (!val)
       continue;
     result[optionalProperty] = val;
   }
   return result;
 }
 function _usedThemesExceptId(aId)
   LightweightThemeManager.usedThemes.filter(
        function usedThemesExceptId_filterID(t) "id" in t && t.id != aId);
 function _version(aThemeData)
   aThemeData.version || "";
 function _makeURI(aURL, aBaseURI)
   Services.io.newURI(aURL, null, aBaseURI);
 function _updateUsedThemes(aList) {
   // Send uninstall events for all themes that need to be removed.
   while (aList.length > _maxUsedThemes) {
     let wrapper = new AddonWrapper(aList[aList.length - 1]);
     AddonManagerPrivate.callAddonListeners("onUninstalling", wrapper, false);
     aList.pop();
     AddonManagerPrivate.callAddonListeners("onUninstalled", wrapper);
   }
   var str = Cc["@mozilla.org/supports-string;1"]
               .createInstance(Ci.nsISupportsString);
   str.data = JSON.stringify(aList);
   _prefs.setComplexValue("usedThemes", Ci.nsISupportsString, str);
   Services.obs.notifyObservers(null, "lightweight-theme-list-changed", null);
 }
 function _notifyWindows(aThemeData) {
   Services.obs.notifyObservers(null, "lightweight-theme-styling-update",
                                JSON.stringify(aThemeData));
 }
 var _previewTimer;
 var _previewTimerCallback = {
   notify: function _previewTimerCallback_notify() {
     LightweightThemeManager.resetPreview();
   }
 };
 /**
  * Called when any of the lightweightThemes preferences are changed.
  */
 function _prefObserver(aSubject, aTopic, aData) {
   switch (aData) {
     case "maxUsedThemes":
       try {
         _maxUsedThemes = _prefs.getIntPref(aData);
       }
       catch (e) {
         _maxUsedThemes = DEFAULT_MAX_USED_THEMES_COUNT;
       }
       // Update the theme list to remove any themes over the number we keep
       _updateUsedThemes(LightweightThemeManager.usedThemes);
       break;
   }
 }
 function _persistImages(aData, aCallback) {
   function onSuccess(key) function () {
     let current = LightweightThemeManager.currentTheme;
     if (current && current.id == aData.id) {
       _prefs.setBoolPref("persisted." + key, true);
     }
     if (--numFilesToPersist == 0 && aCallback) {
       aCallback();
     }
   };
   let numFilesToPersist = 0;
   for (let key in PERSIST_FILES) {
     _prefs.setBoolPref("persisted." + key, false);
     if (aData[key]) {
       numFilesToPersist++;
       _persistImage(aData[key], PERSIST_FILES[key], onSuccess(key));
     }
   }
 }
 function _getLocalImageURI(localFileName) {
   var localFile = Services.dirsvc.get("ProfD", Ci.nsIFile);
   localFile.append(localFileName);
   return Services.io.newFileURI(localFile);
 }
 function _persistImage(sourceURL, localFileName, successCallback) {
   if (/^file:/.test(sourceURL))
     return;
   var targetURI = _getLocalImageURI(localFileName);
   var sourceURI = _makeURI(sourceURL);
   var persist = Cc["@mozilla.org/embedding/browser/nsWebBrowserPersist;1"]
                   .createInstance(Ci.nsIWebBrowserPersist);
   persist.persistFlags =
     Ci.nsIWebBrowserPersist.PERSIST_FLAGS_REPLACE_EXISTING_FILES |
     Ci.nsIWebBrowserPersist.PERSIST_FLAGS_AUTODETECT_APPLY_CONVERSION |
     (PERSIST_BYPASS_CACHE ?
        Ci.nsIWebBrowserPersist.PERSIST_FLAGS_BYPASS_CACHE :
        Ci.nsIWebBrowserPersist.PERSIST_FLAGS_FROM_CACHE);
   persist.progressListener = new _persistProgressListener(successCallback);
   persist.saveURI(sourceURI, null, null, null, null, targetURI, null);
 }
 function _persistProgressListener(successCallback) {
   this.onLocationChange = function persistProgressListener_onLocationChange() {};
   this.onProgressChange = function persistProgressListener_onProgressChange() {};
   this.onStatusChange   = function persistProgressListener_onStatusChange() {};
   this.onSecurityChange = function persistProgressListener_onSecurityChange() {};
   this.onStateChange    = function persistProgressListener_onStateChange(aWebProgress, aRequest, aStateFlags, aStatus) {
     if (aRequest &&
         aStateFlags & Ci.nsIWebProgressListener.STATE_IS_NETWORK &&
         aStateFlags & Ci.nsIWebProgressListener.STATE_STOP) {
       try {
         if (aRequest.QueryInterface(Ci.nsIHttpChannel).requestSucceeded) {
           // success
           successCallback();
           return;
         }
       } catch (e) { }
       // failure
     }
   };
 }
 AddonManagerPrivate.registerProvider(LightweightThemeManager, [
   new AddonManagerPrivate.AddonType("theme", URI_EXTENSION_STRINGS,
                                     STRING_TYPE_NAME,
                                     AddonManager.VIEW_TYPE_LIST, 5000)
 ]);

The Tor Browser / annotate

toolkit/mozapps/extensions/LightweightThemeManager.jsm@6474c204b198 (annotated)

toolkit/mozapps/extensions/LightweightThemeManager.jsm