The Tor Browser: browser/components/feeds/src/WebContentConverter.js@6474c204b198 (annotated)

browser/components/feeds/src/WebContentConverter.js@6474c204b198 (annotated)

browser/components/feeds/src/WebContentConverter.js

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.

 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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/. */
 Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
 Components.utils.import("resource://gre/modules/PrivateBrowsingUtils.jsm");
 const Cc = Components.classes;
 const Ci = Components.interfaces;
 const Cr = Components.results;
 function LOG(str) {
   dump("*** " + str + "\n");
 }
 const WCCR_CONTRACTID = "@mozilla.org/embeddor.implemented/web-content-handler-registrar;1";
 const WCCR_CLASSID = Components.ID("{792a7e82-06a0-437c-af63-b2d12e808acc}");
 const WCC_CLASSID = Components.ID("{db7ebf28-cc40-415f-8a51-1b111851df1e}");
 const WCC_CLASSNAME = "Web Service Handler";
 const TYPE_MAYBE_FEED = "application/vnd.mozilla.maybe.feed";
 const TYPE_ANY = "*/*";
 const PREF_CONTENTHANDLERS_AUTO = "browser.contentHandlers.auto.";
 const PREF_CONTENTHANDLERS_BRANCH = "browser.contentHandlers.types.";
 const PREF_SELECTED_WEB = "browser.feeds.handlers.webservice";
 const PREF_SELECTED_ACTION = "browser.feeds.handler";
 const PREF_SELECTED_READER = "browser.feeds.handler.default";
 const PREF_HANDLER_EXTERNAL_PREFIX = "network.protocol-handler.external";
 const PREF_ALLOW_DIFFERENT_HOST = "gecko.handlerService.allowRegisterFromDifferentHost";
 const STRING_BUNDLE_URI = "chrome://browser/locale/feeds/subscribe.properties";
 const NS_ERROR_MODULE_DOM = 2152923136;
 const NS_ERROR_DOM_SYNTAX_ERR = NS_ERROR_MODULE_DOM + 12;
 function WebContentConverter() {
 }
 WebContentConverter.prototype = {
   convert: function WCC_convert() { },
   asyncConvertData: function WCC_asyncConvertData() { },
   onDataAvailable: function WCC_onDataAvailable() { },
   onStopRequest: function WCC_onStopRequest() { },
   onStartRequest: function WCC_onStartRequest(request, context) {
     var wccr =
         Cc[WCCR_CONTRACTID].
         getService(Ci.nsIWebContentConverterService);
     wccr.loadPreferredHandler(request);
   },
   QueryInterface: function WCC_QueryInterface(iid) {
     if (iid.equals(Ci.nsIStreamConverter) ||
         iid.equals(Ci.nsIStreamListener) ||
         iid.equals(Ci.nsISupports))
       return this;
     throw Cr.NS_ERROR_NO_INTERFACE;
   }
 };
 var WebContentConverterFactory = {
   createInstance: function WCCF_createInstance(outer, iid) {
     if (outer != null)
       throw Cr.NS_ERROR_NO_AGGREGATION;
     return new WebContentConverter().QueryInterface(iid);
   },
   QueryInterface: function WCC_QueryInterface(iid) {
     if (iid.equals(Ci.nsIFactory) ||
         iid.equals(Ci.nsISupports))
       return this;
     throw Cr.NS_ERROR_NO_INTERFACE;
   }
 };
 function ServiceInfo(contentType, uri, name) {
   this._contentType = contentType;
   this._uri = uri;
   this._name = name;
 }
 ServiceInfo.prototype = {
   /**
    * See nsIHandlerApp
    */
   get name() {
     return this._name;
   },
   /**
    * See nsIHandlerApp
    */
   equals: function SI_equals(aHandlerApp) {
     if (!aHandlerApp)
       throw Cr.NS_ERROR_NULL_POINTER;
     if (aHandlerApp instanceof Ci.nsIWebContentHandlerInfo &&
         aHandlerApp.contentType == this.contentType &&
         aHandlerApp.uri == this.uri)
       return true;
     return false;
   },
   /**
    * See nsIWebContentHandlerInfo
    */
   get contentType() {
     return this._contentType;
   },
   /**
    * See nsIWebContentHandlerInfo
    */
   get uri() {
     return this._uri;
   },
   /**
    * See nsIWebContentHandlerInfo
    */
   getHandlerURI: function SI_getHandlerURI(uri) {
     return this._uri.replace(/%s/gi, encodeURIComponent(uri));
   },
   QueryInterface: function SI_QueryInterface(iid) {
     if (iid.equals(Ci.nsIWebContentHandlerInfo) ||
         iid.equals(Ci.nsISupports))
       return this;
     throw Cr.NS_ERROR_NO_INTERFACE;
   }
 };
 function WebContentConverterRegistrar() {
   this._contentTypes = { };
   this._autoHandleContentTypes = { };
 }
 WebContentConverterRegistrar.prototype = {
   get stringBundle() {
     var sb = Cc["@mozilla.org/intl/stringbundle;1"].
               getService(Ci.nsIStringBundleService).
               createBundle(STRING_BUNDLE_URI);
     delete WebContentConverterRegistrar.prototype.stringBundle;
     return WebContentConverterRegistrar.prototype.stringBundle = sb;
   },
   _getFormattedString: function WCCR__getFormattedString(key, params) {
     return this.stringBundle.formatStringFromName(key, params, params.length);
   },
   _getString: function WCCR_getString(key) {
     return this.stringBundle.GetStringFromName(key);
   },
   /**
    * See nsIWebContentConverterService
    */
   getAutoHandler:
   function WCCR_getAutoHandler(contentType) {
     contentType = this._resolveContentType(contentType);
     if (contentType in this._autoHandleContentTypes)
       return this._autoHandleContentTypes[contentType];
     return null;
   },
   /**
    * See nsIWebContentConverterService
    */
   setAutoHandler:
   function WCCR_setAutoHandler(contentType, handler) {
     if (handler && !this._typeIsRegistered(contentType, handler.uri))
       throw Cr.NS_ERROR_NOT_AVAILABLE;
     contentType = this._resolveContentType(contentType);
     this._setAutoHandler(contentType, handler);
     var ps =
         Cc["@mozilla.org/preferences-service;1"].
         getService(Ci.nsIPrefService);
     var autoBranch = ps.getBranch(PREF_CONTENTHANDLERS_AUTO);
     if (handler)
       autoBranch.setCharPref(contentType, handler.uri);
     else if (autoBranch.prefHasUserValue(contentType))
       autoBranch.clearUserPref(contentType);
     ps.savePrefFile(null);
   },
   /**
    * Update the internal data structure (not persistent)
    */
   _setAutoHandler:
   function WCCR__setAutoHandler(contentType, handler) {
     if (handler)
       this._autoHandleContentTypes[contentType] = handler;
     else if (contentType in this._autoHandleContentTypes)
       delete this._autoHandleContentTypes[contentType];
   },
   /**
    * See nsIWebContentConverterService
    */
   getWebContentHandlerByURI:
   function WCCR_getWebContentHandlerByURI(contentType, uri) {
     var handlers = this.getContentHandlers(contentType, { });
     for (var i = 0; i < handlers.length; ++i) {
       if (handlers[i].uri == uri)
         return handlers[i];
     }
     return null;
   },
   /**
    * See nsIWebContentConverterService
    */
   loadPreferredHandler:
   function WCCR_loadPreferredHandler(request) {
     var channel = request.QueryInterface(Ci.nsIChannel);
     var contentType = this._resolveContentType(channel.contentType);
     var handler = this.getAutoHandler(contentType);
     if (handler) {
       request.cancel(Cr.NS_ERROR_FAILURE);
       var webNavigation =
           channel.notificationCallbacks.getInterface(Ci.nsIWebNavigation);
       webNavigation.loadURI(handler.getHandlerURI(channel.URI.spec),
                             Ci.nsIWebNavigation.LOAD_FLAGS_NONE,
                             null, null, null);
     }
   },
   /**
    * See nsIWebContentConverterService
    */
   removeProtocolHandler:
   function WCCR_removeProtocolHandler(aProtocol, aURITemplate) {
     var eps = Cc["@mozilla.org/uriloader/external-protocol-service;1"].
               getService(Ci.nsIExternalProtocolService);
     var handlerInfo = eps.getProtocolHandlerInfo(aProtocol);
     var handlers =  handlerInfo.possibleApplicationHandlers;
     for (let i = 0; i < handlers.length; i++) {
       try { // We only want to test web handlers
         let handler = handlers.queryElementAt(i, Ci.nsIWebHandlerApp);
         if (handler.uriTemplate == aURITemplate) {
           handlers.removeElementAt(i);
           var hs = Cc["@mozilla.org/uriloader/handler-service;1"].
                    getService(Ci.nsIHandlerService);
           hs.store(handlerInfo);
           return;
         }
       } catch (e) { /* it wasn't a web handler */ }
     }
   },
   /**
    * See nsIWebContentConverterService
    */
   removeContentHandler:
   function WCCR_removeContentHandler(contentType, uri) {
     function notURI(serviceInfo) {
       return serviceInfo.uri != uri;
     }
     if (contentType in this._contentTypes) {
       this._contentTypes[contentType] =
         this._contentTypes[contentType].filter(notURI);
     }
   },
   /**
    *
    */
   _mappings: {
     "application/rss+xml": TYPE_MAYBE_FEED,
     "application/atom+xml": TYPE_MAYBE_FEED,
   },
   /**
    * These are types for which there is a separate content converter aside
    * from our built in generic one. We should not automatically register
    * a factory for creating a converter for these types.
    */
   _blockedTypes: {
     "application/vnd.mozilla.maybe.feed": true,
   },
   /**
    * Determines the "internal" content type based on the _mappings.
    * @param   contentType
    * @returns The resolved contentType value.
    */
   _resolveContentType:
   function WCCR__resolveContentType(contentType) {
     if (contentType in this._mappings)
       return this._mappings[contentType];
     return contentType;
   },
   _makeURI: function(aURL, aOriginCharset, aBaseURI) {
     var ioService = Components.classes["@mozilla.org/network/io-service;1"]
                               .getService(Components.interfaces.nsIIOService);
     return ioService.newURI(aURL, aOriginCharset, aBaseURI);
   },
   _checkAndGetURI:
   function WCCR_checkAndGetURI(aURIString, aContentWindow)
   {
     try {
       let baseURI = aContentWindow.document.baseURIObject;
       var uri = this._makeURI(aURIString, null, baseURI);
     } catch (ex) {
       // not supposed to throw according to spec
       return;
     }
     // For security reasons we reject non-http(s) urls (see bug 354316),
     // we may need to revise this once we support more content types
     // XXX this should be a "security exception" according to spec, but that
     // isn't defined yet.
     if (uri.scheme != "http" && uri.scheme != "https")
       throw("Permission denied to add " + uri.spec + " as a content or protocol handler");
     // We also reject handlers registered from a different host (see bug 402287)
     // The pref allows us to test the feature
     var pb = Cc["@mozilla.org/preferences-service;1"].getService(Ci.nsIPrefBranch);
     if ((!pb.prefHasUserValue(PREF_ALLOW_DIFFERENT_HOST) ||
          !pb.getBoolPref(PREF_ALLOW_DIFFERENT_HOST)) &&
         aContentWindow.location.hostname != uri.host)
       throw("Permission denied to add " + uri.spec + " as a content or protocol handler");
     // If the uri doesn't contain '%s', it won't be a good handler
     if (uri.spec.indexOf("%s") < 0)
       throw NS_ERROR_DOM_SYNTAX_ERR;
     return uri;
   },
   /**
    * Determines if a web handler is already registered.
    *
    * @param aProtocol
    *        The scheme of the web handler we are checking for.
    * @param aURITemplate
    *        The URI template that the handler uses to handle the protocol.
    * @return true if it is already registered, false otherwise.
    */
   _protocolHandlerRegistered:
   function WCCR_protocolHandlerRegistered(aProtocol, aURITemplate) {
     var eps = Cc["@mozilla.org/uriloader/external-protocol-service;1"].
               getService(Ci.nsIExternalProtocolService);
     var handlerInfo = eps.getProtocolHandlerInfo(aProtocol);
     var handlers =  handlerInfo.possibleApplicationHandlers;
     for (let i = 0; i < handlers.length; i++) {
       try { // We only want to test web handlers
         let handler = handlers.queryElementAt(i, Ci.nsIWebHandlerApp);
         if (handler.uriTemplate == aURITemplate)
           return true;
       } catch (e) { /* it wasn't a web handler */ }
     }
     return false;
   },
   /**
    * See nsIWebContentHandlerRegistrar
    */
   registerProtocolHandler:
   function WCCR_registerProtocolHandler(aProtocol, aURIString, aTitle, aContentWindow) {
     LOG("registerProtocolHandler(" + aProtocol + "," + aURIString + "," + aTitle + ")");
     var uri = this._checkAndGetURI(aURIString, aContentWindow);
     // If the protocol handler is already registered, just return early.
     if (this._protocolHandlerRegistered(aProtocol, uri.spec)) {
       return;
     }
     var browserWindow = this._getBrowserWindowForContentWindow(aContentWindow);
     if (PrivateBrowsingUtils.isWindowPrivate(browserWindow)) {
       // Inside the private browsing mode, we don't want to alert the user to save
       // a protocol handler.  We log it to the error console so that web developers
       // would have some way to tell what's going wrong.
       Cc["@mozilla.org/consoleservice;1"].
       getService(Ci.nsIConsoleService).
       logStringMessage("Web page denied access to register a protocol handler inside private browsing mode");
       return;
     }
     // First, check to make sure this isn't already handled internally (we don't
     // want to let them take over, say "chrome").
     var ios = Cc["@mozilla.org/network/io-service;1"].
               getService(Ci.nsIIOService);
     var handler = ios.getProtocolHandler(aProtocol);
     if (!(handler instanceof Ci.nsIExternalProtocolHandler)) {
       // This is handled internally, so we don't want them to register
       // XXX this should be a "security exception" according to spec, but that
       // isn't defined yet.
       throw("Permission denied to add " + aURIString + "as a protocol handler");
     }
     // check if it is in the black list
     var pb = Cc["@mozilla.org/preferences-service;1"].getService(Ci.nsIPrefBranch);
     var allowed;
     try {
       allowed = pb.getBoolPref(PREF_HANDLER_EXTERNAL_PREFIX + "." + aProtocol);
     }
     catch (e) {
       allowed = pb.getBoolPref(PREF_HANDLER_EXTERNAL_PREFIX + "-default");
     }
     if (!allowed) {
       // XXX this should be a "security exception" according to spec
       throw("Not allowed to register a protocol handler for " + aProtocol);
     }
     // Now Ask the user and provide the proper callback
     var message = this._getFormattedString("addProtocolHandler",
                                            [aTitle, uri.host, aProtocol]);
     var notificationIcon = uri.prePath + "/favicon.ico";
     var notificationValue = "Protocol Registration: " + aProtocol;
     var addButton = {
       label: this._getString("addProtocolHandlerAddButton"),
       accessKey: this._getString("addHandlerAddButtonAccesskey"),
       protocolInfo: { protocol: aProtocol, uri: uri.spec, name: aTitle },
       callback:
         function WCCR_addProtocolHandlerButtonCallback(aNotification, aButtonInfo) {
           var protocol = aButtonInfo.protocolInfo.protocol;
           var uri      = aButtonInfo.protocolInfo.uri;
           var name     = aButtonInfo.protocolInfo.name;
           var handler = Cc["@mozilla.org/uriloader/web-handler-app;1"].
                         createInstance(Ci.nsIWebHandlerApp);
           handler.name = name;
           handler.uriTemplate = uri;
           var eps = Cc["@mozilla.org/uriloader/external-protocol-service;1"].
                     getService(Ci.nsIExternalProtocolService);
           var handlerInfo = eps.getProtocolHandlerInfo(protocol);
           handlerInfo.possibleApplicationHandlers.appendElement(handler, false);
           // Since the user has agreed to add a new handler, chances are good
           // that the next time they see a handler of this type, they're going
           // to want to use it.  Reset the handlerInfo to ask before the next
           // use.
           handlerInfo.alwaysAskBeforeHandling = true;
           var hs = Cc["@mozilla.org/uriloader/handler-service;1"].
                    getService(Ci.nsIHandlerService);
           hs.store(handlerInfo);
         }
     };
     var browserElement = this._getBrowserForContentWindow(browserWindow, aContentWindow);
     var notificationBox = browserWindow.getBrowser().getNotificationBox(browserElement);
     notificationBox.appendNotification(message,
                                        notificationValue,
                                        notificationIcon,
                                        notificationBox.PRIORITY_INFO_LOW,
                                        [addButton]);
   },
   /**
    * See nsIWebContentHandlerRegistrar
    * If a DOM window is provided, then the request came from content, so we
    * prompt the user to confirm the registration.
    */
   registerContentHandler:
   function WCCR_registerContentHandler(aContentType, aURIString, aTitle, aContentWindow) {
     LOG("registerContentHandler(" + aContentType + "," + aURIString + "," + aTitle + ")");
     // We only support feed types at present.
     // XXX this should be a "security exception" according to spec, but that
     // isn't defined yet.
     var contentType = this._resolveContentType(aContentType);
     if (contentType != TYPE_MAYBE_FEED)
       return;
     if (aContentWindow) {
       var uri = this._checkAndGetURI(aURIString, aContentWindow);
       var browserWindow = this._getBrowserWindowForContentWindow(aContentWindow);
       var browserElement = this._getBrowserForContentWindow(browserWindow, aContentWindow);
       var notificationBox = browserWindow.getBrowser().getNotificationBox(browserElement);
       this._appendFeedReaderNotification(uri, aTitle, notificationBox);
     }
     else
       this._registerContentHandler(contentType, aURIString, aTitle);
   },
   /**
    * Returns the browser chrome window in which the content window is in
    */
   _getBrowserWindowForContentWindow:
   function WCCR__getBrowserWindowForContentWindow(aContentWindow) {
     return aContentWindow.QueryInterface(Ci.nsIInterfaceRequestor)
                          .getInterface(Ci.nsIWebNavigation)
                          .QueryInterface(Ci.nsIDocShellTreeItem)
                          .rootTreeItem
                          .QueryInterface(Ci.nsIInterfaceRequestor)
                          .getInterface(Ci.nsIDOMWindow)
                          .wrappedJSObject;
   },
   /**
    * Returns the <xul:browser> element associated with the given content
    * window.
    *
    * @param aBrowserWindow
    *        The browser window in which the content window is in.
    * @param aContentWindow
    *        The content window. It's possible to pass a child content window
    *        (i.e. the content window of a frame/iframe).
    */
   _getBrowserForContentWindow:
   function WCCR__getBrowserForContentWindow(aBrowserWindow, aContentWindow) {
     // This depends on pseudo APIs of browser.js and tabbrowser.xml
     aContentWindow = aContentWindow.top;
     var browsers = aBrowserWindow.getBrowser().browsers;
     for (var i = 0; i < browsers.length; ++i) {
       if (browsers[i].contentWindow == aContentWindow)
         return browsers[i];
     }
   },
   /**
    * Appends a notifcation for the given feed reader details.
    *
    * The notification could be either a pseudo-dialog which lets
    * the user to add the feed reader:
    * [ [icon] Add %feed-reader-name% (%feed-reader-host%) as a Feed Reader?  (Add) [x] ]
    *
    * or a simple message for the case where the feed reader is already registered:
    * [ [icon] %feed-reader-name% is already registered as a Feed Reader             [x] ]
    *
    * A new notification isn't appended if the given notificationbox has a
    * notification for the same feed reader.
    *
    * @param aURI
    *        The url of the feed reader as a nsIURI object
    * @param aName
    *        The feed reader name as it was passed to registerContentHandler
    * @param aNotificationBox
    *        The notification box to which a notification might be appended
    * @return true if a notification has been appended, false otherwise.
    */
   _appendFeedReaderNotification:
   function WCCR__appendFeedReaderNotification(aURI, aName, aNotificationBox) {
     var uriSpec = aURI.spec;
     var notificationValue = "feed reader notification: " + uriSpec;
     var notificationIcon = aURI.prePath + "/favicon.ico";
     // Don't append a new notification if the notificationbox
     // has a notification for the given feed reader already
     if (aNotificationBox.getNotificationWithValue(notificationValue))
       return false;
     var buttons, message;
     if (this.getWebContentHandlerByURI(TYPE_MAYBE_FEED, uriSpec))
       message = this._getFormattedString("handlerRegistered", [aName]);
     else {
       message = this._getFormattedString("addHandler", [aName, aURI.host]);
       var self = this;
       var addButton = {
         _outer: self,
         label: self._getString("addHandlerAddButton"),
         accessKey: self._getString("addHandlerAddButtonAccesskey"),
         feedReaderInfo: { uri: uriSpec, name: aName },
         /* static */
         callback:
         function WCCR__addFeedReaderButtonCallback(aNotification, aButtonInfo) {
           var uri = aButtonInfo.feedReaderInfo.uri;
           var name = aButtonInfo.feedReaderInfo.name;
           var outer = aButtonInfo._outer;
           // The reader could have been added from another window mean while
           if (!outer.getWebContentHandlerByURI(TYPE_MAYBE_FEED, uri))
             outer._registerContentHandler(TYPE_MAYBE_FEED, uri, name);
           // avoid reference cycles
           aButtonInfo._outer = null;
           return false;
         }
       };
       buttons = [addButton];
     }
     aNotificationBox.appendNotification(message,
                                         notificationValue,
                                         notificationIcon,
                                         aNotificationBox.PRIORITY_INFO_LOW,
                                         buttons);
     return true;
   },
   /**
    * Save Web Content Handler metadata to persistent preferences.
    * @param   contentType
    *          The content Type being handled
    * @param   uri
    *          The uri of the web service
    * @param   title
    *          The human readable name of the web service
    *
    * This data is stored under:
    *
    *    browser.contentHandlers.type0 = content/type
    *    browser.contentHandlers.uri0 = http://www.foo.com/q=%s
    *    browser.contentHandlers.title0 = Foo 2.0alphr
    */
   _saveContentHandlerToPrefs:
   function WCCR__saveContentHandlerToPrefs(contentType, uri, title) {
     var ps =
         Cc["@mozilla.org/preferences-service;1"].
         getService(Ci.nsIPrefService);
     var i = 0;
     var typeBranch = null;
     while (true) {
       typeBranch =
         ps.getBranch(PREF_CONTENTHANDLERS_BRANCH + i + ".");
       try {
         typeBranch.getCharPref("type");
         ++i;
       }
       catch (e) {
         // No more handlers
         break;
       }
     }
     if (typeBranch) {
       typeBranch.setCharPref("type", contentType);
       var pls =
           Cc["@mozilla.org/pref-localizedstring;1"].
           createInstance(Ci.nsIPrefLocalizedString);
       pls.data = uri;
       typeBranch.setComplexValue("uri", Ci.nsIPrefLocalizedString, pls);
       pls.data = title;
       typeBranch.setComplexValue("title", Ci.nsIPrefLocalizedString, pls);
       ps.savePrefFile(null);
     }
   },
   /**
    * Determines if there is a type with a particular uri registered for the
    * specified content type already.
    * @param   contentType
    *          The content type that the uri handles
    * @param   uri
    *          The uri of the
    */
   _typeIsRegistered: function WCCR__typeIsRegistered(contentType, uri) {
     if (!(contentType in this._contentTypes))
       return false;
     var services = this._contentTypes[contentType];
     for (var i = 0; i < services.length; ++i) {
       // This uri has already been registered
       if (services[i].uri == uri)
         return true;
     }
     return false;
   },
   /**
    * Gets a stream converter contract id for the specified content type.
    * @param   contentType
    *          The source content type for the conversion.
    * @returns A contract id to construct a converter to convert between the
    *          contentType and *\/*.
    */
   _getConverterContractID: function WCCR__getConverterContractID(contentType) {
     const template = "@mozilla.org/streamconv;1?from=%s&to=*/*";
     return template.replace(/%s/, contentType);
   },
   /**
    * Register a web service handler for a content type.
    *
    * @param   contentType
    *          the content type being handled
    * @param   uri
    *          the URI of the web service
    * @param   title
    *          the human readable name of the web service
    */
   _registerContentHandler:
   function WCCR__registerContentHandler(contentType, uri, title) {
     this._updateContentTypeHandlerMap(contentType, uri, title);
     this._saveContentHandlerToPrefs(contentType, uri, title);
     if (contentType == TYPE_MAYBE_FEED) {
       // Make the new handler the last-selected reader in the preview page
       // and make sure the preview page is shown the next time a feed is visited
       var pb = Cc["@mozilla.org/preferences-service;1"].
                getService(Ci.nsIPrefService).getBranch(null);
       pb.setCharPref(PREF_SELECTED_READER, "web");
       var supportsString =
         Cc["@mozilla.org/supports-string;1"].
         createInstance(Ci.nsISupportsString);
         supportsString.data = uri;
       pb.setComplexValue(PREF_SELECTED_WEB, Ci.nsISupportsString,
                          supportsString);
       pb.setCharPref(PREF_SELECTED_ACTION, "ask");
       this._setAutoHandler(TYPE_MAYBE_FEED, null);
     }
   },
   /**
    * Update the content type -> handler map. This mapping is not persisted, use
    * registerContentHandler or _saveContentHandlerToPrefs for that purpose.
    * @param   contentType
    *          The content Type being handled
    * @param   uri
    *          The uri of the web service
    * @param   title
    *          The human readable name of the web service
    */
   _updateContentTypeHandlerMap:
   function WCCR__updateContentTypeHandlerMap(contentType, uri, title) {
     if (!(contentType in this._contentTypes))
       this._contentTypes[contentType] = [];
     // Avoid adding duplicates
     if (this._typeIsRegistered(contentType, uri))
       return;
     this._contentTypes[contentType].push(new ServiceInfo(contentType, uri, title));
     if (!(contentType in this._blockedTypes)) {
       var converterContractID = this._getConverterContractID(contentType);
       var cr = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
       cr.registerFactory(WCC_CLASSID, WCC_CLASSNAME, converterContractID,
                          WebContentConverterFactory);
     }
   },
   /**
    * See nsIWebContentConverterService
    */
   getContentHandlers:
   function WCCR_getContentHandlers(contentType, countRef) {
     countRef.value = 0;
     if (!(contentType in this._contentTypes))
       return [];
     var handlers = this._contentTypes[contentType];
     countRef.value = handlers.length;
     return handlers;
   },
   /**
    * See nsIWebContentConverterService
    */
   resetHandlersForType:
   function WCCR_resetHandlersForType(contentType) {
     // currently unused within the tree, so only useful for extensions; previous
     // impl. was buggy (and even infinite-looped!), so I argue that this is a
     // definite improvement
     throw Cr.NS_ERROR_NOT_IMPLEMENTED;
   },
   /**
    * Registers a handler from the settings on a preferences branch.
    *
    * @param branch
    *        an nsIPrefBranch containing "type", "uri", and "title" preferences
    *        corresponding to the content handler to be registered
    */
   _registerContentHandlerWithBranch: function(branch) {
     /**
      * Since we support up to six predefined readers, we need to handle gaps
      * better, since the first branch with user-added values will be .6
      *
      * How we deal with that is to check to see if there's no prefs in the
      * branch and stop cycling once that's true.  This doesn't fix the case
      * where a user manually removes a reader, but that's not supported yet!
      */
     var vals = branch.getChildList("");
     if (vals.length == 0)
       return;
     try {
       var type = branch.getCharPref("type");
       var uri = branch.getComplexValue("uri", Ci.nsIPrefLocalizedString).data;
       var title = branch.getComplexValue("title",
                                          Ci.nsIPrefLocalizedString).data;
       this._updateContentTypeHandlerMap(type, uri, title);
     }
     catch(ex) {
       // do nothing, the next branch might have values
     }
   },
   /**
    * Load the auto handler, content handler and protocol tables from
    * preferences.
    */
   _init: function WCCR__init() {
     var ps =
         Cc["@mozilla.org/preferences-service;1"].
         getService(Ci.nsIPrefService);
     var kids = ps.getBranch(PREF_CONTENTHANDLERS_BRANCH)
                  .getChildList("");
     // first get the numbers of the providers by getting all ###.uri prefs
     var nums = [];
     for (var i = 0; i < kids.length; i++) {
       var match = /^(\d+)\.uri$/.exec(kids[i]);
       if (!match)
         continue;
       else
         nums.push(match[1]);
     }
     // sort them, to get them back in order
     nums.sort(function(a, b) {return a - b;});
     // now register them
     for (var i = 0; i < nums.length; i++) {
       var branch = ps.getBranch(PREF_CONTENTHANDLERS_BRANCH + nums[i] + ".");
       this._registerContentHandlerWithBranch(branch);
     }
     // We need to do this _after_ registering all of the available handlers,
     // so that getWebContentHandlerByURI can return successfully.
     try {
       var autoBranch = ps.getBranch(PREF_CONTENTHANDLERS_AUTO);
       var childPrefs = autoBranch.getChildList("");
       for (var i = 0; i < childPrefs.length; ++i) {
         var type = childPrefs[i];
         var uri = autoBranch.getCharPref(type);
         if (uri) {
           var handler = this.getWebContentHandlerByURI(type, uri);
           this._setAutoHandler(type, handler);
         }
       }
     }
     catch (e) {
       // No auto branch yet, that's fine
       //LOG("WCCR.init: There is no auto branch, benign");
     }
   },
   /**
    * See nsIObserver
    */
   observe: function WCCR_observe(subject, topic, data) {
     var os =
         Cc["@mozilla.org/observer-service;1"].
         getService(Ci.nsIObserverService);
     switch (topic) {
     case "app-startup":
       os.addObserver(this, "browser-ui-startup-complete", false);
       break;
     case "browser-ui-startup-complete":
       os.removeObserver(this, "browser-ui-startup-complete");
       this._init();
       break;
     }
   },
   /**
    * See nsIFactory
    */
   createInstance: function WCCR_createInstance(outer, iid) {
     if (outer != null)
       throw Cr.NS_ERROR_NO_AGGREGATION;
     return this.QueryInterface(iid);
   },
   classID: WCCR_CLASSID,
   /**
    * See nsISupports
    */
   QueryInterface: XPCOMUtils.generateQI(
      [Ci.nsIWebContentConverterService,
       Ci.nsIWebContentHandlerRegistrar,
       Ci.nsIObserver,
       Ci.nsIFactory]),
   _xpcom_categories: [{
     category: "app-startup",
     service: true
   }]
 };
 this.NSGetFactory = XPCOMUtils.generateNSGetFactory([WebContentConverterRegistrar]);