Add m-esr52 at 52.6.0

1 files changed, 1900 insertions, 0 deletions

diff --git a/browser/components/preferences/in-content/applications.js b/browser/components/preferences/in-content/applications.js
new file mode 100644
index 000000000..6f2989657
--- /dev/null
+++ b/browser/components/preferences/in-content/applications.js
@@ -0,0 +1,1900 @@
+/* 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";
+
+// Constants & Enumeration Values
+
+Components.utils.import('resource://gre/modules/Services.jsm');
+Components.utils.import('resource://gre/modules/AppConstants.jsm');
+const TYPE_MAYBE_FEED = "application/vnd.mozilla.maybe.feed";
+const TYPE_MAYBE_VIDEO_FEED = "application/vnd.mozilla.maybe.video.feed";
+const TYPE_MAYBE_AUDIO_FEED = "application/vnd.mozilla.maybe.audio.feed";
+const TYPE_PDF = "application/pdf";
+
+const PREF_PDFJS_DISABLED = "pdfjs.disabled";
+const TOPIC_PDFJS_HANDLER_CHANGED = "pdfjs:handlerChanged";
+
+const PREF_DISABLED_PLUGIN_TYPES = "plugin.disable_full_page_plugin_for_types";
+
+// Preferences that affect which entries to show in the list.
+const PREF_SHOW_PLUGINS_IN_LIST = "browser.download.show_plugins_in_list";
+const PREF_HIDE_PLUGINS_WITHOUT_EXTENSIONS =
+  "browser.download.hide_plugins_without_extensions";
+
+/*
+ * Preferences where we store handling information about the feed type.
+ *
+ * browser.feeds.handler
+ * - "bookmarks", "reader" (clarified further using the .default preference),
+ *   or "ask" -- indicates the default handler being used to process feeds;
+ *   "bookmarks" is obsolete; to specify that the handler is bookmarks,
+ *   set browser.feeds.handler.default to "bookmarks";
+ *
+ * browser.feeds.handler.default
+ * - "bookmarks", "client" or "web" -- indicates the chosen feed reader used
+ *   to display feeds, either transiently (i.e., when the "use as default"
+ *   checkbox is unchecked, corresponds to when browser.feeds.handler=="ask")
+ *   or more permanently (i.e., the item displayed in the dropdown in Feeds
+ *   preferences)
+ *
+ * browser.feeds.handler.webservice
+ * - the URL of the currently selected web service used to read feeds
+ *
+ * browser.feeds.handlers.application
+ * - nsILocalFile, stores the current client-side feed reading app if one has
+ *   been chosen
+ */
+const PREF_FEED_SELECTED_APP    = "browser.feeds.handlers.application";
+const PREF_FEED_SELECTED_WEB    = "browser.feeds.handlers.webservice";
+const PREF_FEED_SELECTED_ACTION = "browser.feeds.handler";
+const PREF_FEED_SELECTED_READER = "browser.feeds.handler.default";
+
+const PREF_VIDEO_FEED_SELECTED_APP    = "browser.videoFeeds.handlers.application";
+const PREF_VIDEO_FEED_SELECTED_WEB    = "browser.videoFeeds.handlers.webservice";
+const PREF_VIDEO_FEED_SELECTED_ACTION = "browser.videoFeeds.handler";
+const PREF_VIDEO_FEED_SELECTED_READER = "browser.videoFeeds.handler.default";
+
+const PREF_AUDIO_FEED_SELECTED_APP    = "browser.audioFeeds.handlers.application";
+const PREF_AUDIO_FEED_SELECTED_WEB    = "browser.audioFeeds.handlers.webservice";
+const PREF_AUDIO_FEED_SELECTED_ACTION = "browser.audioFeeds.handler";
+const PREF_AUDIO_FEED_SELECTED_READER = "browser.audioFeeds.handler.default";
+
+// The nsHandlerInfoAction enumeration values in nsIHandlerInfo identify
+// the actions the application can take with content of various types.
+// But since nsIHandlerInfo doesn't support plugins, there's no value
+// identifying the "use plugin" action, so we use this constant instead.
+const kActionUsePlugin = 5;
+
+const ICON_URL_APP = AppConstants.platform == "linux" ?
+                     "moz-icon://dummy.exe?size=16" :
+                     "chrome://browser/skin/preferences/application.png";
+
+// For CSS. Can be one of "ask", "save", "plugin" or "feed". If absent, the icon URL
+// was set by us to a custom handler icon and CSS should not try to override it.
+const APP_ICON_ATTR_NAME = "appHandlerIcon";
+
+// Utilities
+
+function getFileDisplayName(file) {
+  if (AppConstants.platform == "win") {
+    if (file instanceof Ci.nsILocalFileWin) {
+      try {
+        return file.getVersionInfoField("FileDescription");
+      } catch (e) {}
+    }
+  }
+  if (AppConstants.platform == "macosx") {
+    if (file instanceof Ci.nsILocalFileMac) {
+      try {
+        return file.bundleDisplayName;
+      } catch (e) {}
+    }
+  }
+  return file.leafName;
+}
+
+function getLocalHandlerApp(aFile) {
+  var localHandlerApp = Cc["@mozilla.org/uriloader/local-handler-app;1"].
+                        createInstance(Ci.nsILocalHandlerApp);
+  localHandlerApp.name = getFileDisplayName(aFile);
+  localHandlerApp.executable = aFile;
+
+  return localHandlerApp;
+}
+
+/**
+ * An enumeration of items in a JS array.
+ *
+ * FIXME: use ArrayConverter once it lands (bug 380839).
+ *
+ * @constructor
+ */
+function ArrayEnumerator(aItems) {
+  this._index = 0;
+  this._contents = aItems;
+}
+
+ArrayEnumerator.prototype = {
+  _index: 0,
+
+  hasMoreElements: function() {
+    return this._index < this._contents.length;
+  },
+
+  getNext: function() {
+    return this._contents[this._index++];
+  }
+};
+
+function isFeedType(t) {
+  return t == TYPE_MAYBE_FEED || t == TYPE_MAYBE_VIDEO_FEED || t == TYPE_MAYBE_AUDIO_FEED;
+}
+
+// HandlerInfoWrapper
+
+/**
+ * This object wraps nsIHandlerInfo with some additional functionality
+ * the Applications prefpane needs to display and allow modification of
+ * the list of handled types.
+ *
+ * We create an instance of this wrapper for each entry we might display
+ * in the prefpane, and we compose the instances from various sources,
+ * including plugins and the handler service.
+ *
+ * We don't implement all the original nsIHandlerInfo functionality,
+ * just the stuff that the prefpane needs.
+ *
+ * In theory, all of the custom functionality in this wrapper should get
+ * pushed down into nsIHandlerInfo eventually.
+ */
+function HandlerInfoWrapper(aType, aHandlerInfo) {
+  this._type = aType;
+  this.wrappedHandlerInfo = aHandlerInfo;
+}
+
+HandlerInfoWrapper.prototype = {
+  // The wrapped nsIHandlerInfo object.  In general, this object is private,
+  // but there are a couple cases where callers access it directly for things
+  // we haven't (yet?) implemented, so we make it a public property.
+  wrappedHandlerInfo: null,
+
+
+  // Convenience Utils
+
+  _handlerSvc: Cc["@mozilla.org/uriloader/handler-service;1"].
+               getService(Ci.nsIHandlerService),
+
+  _prefSvc: Cc["@mozilla.org/preferences-service;1"].
+            getService(Ci.nsIPrefBranch),
+
+  _categoryMgr: Cc["@mozilla.org/categorymanager;1"].
+                getService(Ci.nsICategoryManager),
+
+  element: function(aID) {
+    return document.getElementById(aID);
+  },
+
+
+  // nsIHandlerInfo
+
+  // The MIME type or protocol scheme.
+  _type: null,
+  get type() {
+    return this._type;
+  },
+
+  get description() {
+    if (this.wrappedHandlerInfo.description)
+      return this.wrappedHandlerInfo.description;
+
+    if (this.primaryExtension) {
+      var extension = this.primaryExtension.toUpperCase();
+      return this.element("bundlePreferences").getFormattedString("fileEnding",
+                                                                  [extension]);
+    }
+
+    return this.type;
+  },
+
+  get preferredApplicationHandler() {
+    return this.wrappedHandlerInfo.preferredApplicationHandler;
+  },
+
+  set preferredApplicationHandler(aNewValue) {
+    this.wrappedHandlerInfo.preferredApplicationHandler = aNewValue;
+
+    // Make sure the preferred handler is in the set of possible handlers.
+    if (aNewValue)
+      this.addPossibleApplicationHandler(aNewValue)
+  },
+
+  get possibleApplicationHandlers() {
+    return this.wrappedHandlerInfo.possibleApplicationHandlers;
+  },
+
+  addPossibleApplicationHandler: function(aNewHandler) {
+    var possibleApps = this.possibleApplicationHandlers.enumerate();
+    while (possibleApps.hasMoreElements()) {
+      if (possibleApps.getNext().equals(aNewHandler))
+        return;
+    }
+    this.possibleApplicationHandlers.appendElement(aNewHandler, false);
+  },
+
+  removePossibleApplicationHandler: function(aHandler) {
+    var defaultApp = this.preferredApplicationHandler;
+    if (defaultApp && aHandler.equals(defaultApp)) {
+      // If the app we remove was the default app, we must make sure
+      // it won't be used anymore
+      this.alwaysAskBeforeHandling = true;
+      this.preferredApplicationHandler = null;
+    }
+
+    var handlers = this.possibleApplicationHandlers;
+    for (var i = 0; i < handlers.length; ++i) {
+      var handler = handlers.queryElementAt(i, Ci.nsIHandlerApp);
+      if (handler.equals(aHandler)) {
+        handlers.removeElementAt(i);
+        break;
+      }
+    }
+  },
+
+  get hasDefaultHandler() {
+    return this.wrappedHandlerInfo.hasDefaultHandler;
+  },
+
+  get defaultDescription() {
+    return this.wrappedHandlerInfo.defaultDescription;
+  },
+
+  // What to do with content of this type.
+  get preferredAction() {
+    // If we have an enabled plugin, then the action is to use that plugin.
+    if (this.pluginName && !this.isDisabledPluginType)
+      return kActionUsePlugin;
+
+    // If the action is to use a helper app, but we don't have a preferred
+    // handler app, then switch to using the system default, if any; otherwise
+    // fall back to saving to disk, which is the default action in nsMIMEInfo.
+    // Note: "save to disk" is an invalid value for protocol info objects,
+    // but the alwaysAskBeforeHandling getter will detect that situation
+    // and always return true in that case to override this invalid value.
+    if (this.wrappedHandlerInfo.preferredAction == Ci.nsIHandlerInfo.useHelperApp &&
+        !gApplicationsPane.isValidHandlerApp(this.preferredApplicationHandler)) {
+      if (this.wrappedHandlerInfo.hasDefaultHandler)
+        return Ci.nsIHandlerInfo.useSystemDefault;
+      return Ci.nsIHandlerInfo.saveToDisk;
+    }
+
+    return this.wrappedHandlerInfo.preferredAction;
+  },
+
+  set preferredAction(aNewValue) {
+    // If the action is to use the plugin,
+    // we must set the preferred action to "save to disk".
+    // But only if it's not currently the preferred action.
+    if ((aNewValue == kActionUsePlugin) &&
+        (this.preferredAction != Ci.nsIHandlerInfo.saveToDisk)) {
+      aNewValue = Ci.nsIHandlerInfo.saveToDisk;
+    }
+
+    // We don't modify the preferred action if the new action is to use a plugin
+    // because handler info objects don't understand our custom "use plugin"
+    // value.  Also, leaving it untouched means that we can automatically revert
+    // to the old setting if the user ever removes the plugin.
+
+    if (aNewValue != kActionUsePlugin)
+      this.wrappedHandlerInfo.preferredAction = aNewValue;
+  },
+
+  get alwaysAskBeforeHandling() {
+    // If this type is handled only by a plugin, we can't trust the value
+    // in the handler info object, since it'll be a default based on the absence
+    // of any user configuration, and the default in that case is to always ask,
+    // even though we never ask for content handled by a plugin, so special case
+    // plugin-handled types by returning false here.
+    if (this.pluginName && this.handledOnlyByPlugin)
+      return false;
+
+    // If this is a protocol type and the preferred action is "save to disk",
+    // which is invalid for such types, then return true here to override that
+    // action.  This could happen when the preferred action is to use a helper
+    // app, but the preferredApplicationHandler is invalid, and there isn't
+    // a default handler, so the preferredAction getter returns save to disk
+    // instead.
+    if (!(this.wrappedHandlerInfo instanceof Ci.nsIMIMEInfo) &&
+        this.preferredAction == Ci.nsIHandlerInfo.saveToDisk)
+      return true;
+
+    return this.wrappedHandlerInfo.alwaysAskBeforeHandling;
+  },
+
+  set alwaysAskBeforeHandling(aNewValue) {
+    this.wrappedHandlerInfo.alwaysAskBeforeHandling = aNewValue;
+  },
+
+
+  // nsIMIMEInfo
+
+  // The primary file extension associated with this type, if any.
+  //
+  // XXX Plugin objects contain an array of MimeType objects with "suffixes"
+  // properties; if this object has an associated plugin, shouldn't we check
+  // those properties for an extension?
+  get primaryExtension() {
+    try {
+      if (this.wrappedHandlerInfo instanceof Ci.nsIMIMEInfo &&
+          this.wrappedHandlerInfo.primaryExtension)
+        return this.wrappedHandlerInfo.primaryExtension
+    } catch (ex) {}
+
+    return null;
+  },
+
+
+  // Plugin Handling
+
+  // A plugin that can handle this type, if any.
+  //
+  // Note: just because we have one doesn't mean it *will* handle the type.
+  // That depends on whether or not the type is in the list of types for which
+  // plugin handling is disabled.
+  plugin: null,
+
+  // Whether or not this type is only handled by a plugin or is also handled
+  // by some user-configured action as specified in the handler info object.
+  //
+  // Note: we can't just check if there's a handler info object for this type,
+  // because OS and user configuration is mixed up in the handler info object,
+  // so we always need to retrieve it for the OS info and can't tell whether
+  // it represents only OS-default information or user-configured information.
+  //
+  // FIXME: once handler info records are broken up into OS-provided records
+  // and user-configured records, stop using this boolean flag and simply
+  // check for the presence of a user-configured record to determine whether
+  // or not this type is only handled by a plugin.  Filed as bug 395142.
+  handledOnlyByPlugin: undefined,
+
+  get isDisabledPluginType() {
+    return this._getDisabledPluginTypes().indexOf(this.type) != -1;
+  },
+
+  _getDisabledPluginTypes: function() {
+    var types = "";
+
+    if (this._prefSvc.prefHasUserValue(PREF_DISABLED_PLUGIN_TYPES))
+      types = this._prefSvc.getCharPref(PREF_DISABLED_PLUGIN_TYPES);
+
+    // Only split if the string isn't empty so we don't end up with an array
+    // containing a single empty string.
+    if (types != "")
+      return types.split(",");
+
+    return [];
+  },
+
+  disablePluginType: function() {
+    var disabledPluginTypes = this._getDisabledPluginTypes();
+
+    if (disabledPluginTypes.indexOf(this.type) == -1)
+      disabledPluginTypes.push(this.type);
+
+    this._prefSvc.setCharPref(PREF_DISABLED_PLUGIN_TYPES,
+                              disabledPluginTypes.join(","));
+
+    // Update the category manager so existing browser windows update.
+    this._categoryMgr.deleteCategoryEntry("Gecko-Content-Viewers",
+                                          this.type,
+                                          false);
+  },
+
+  enablePluginType: function() {
+    var disabledPluginTypes = this._getDisabledPluginTypes();
+
+    var type = this.type;
+    disabledPluginTypes = disabledPluginTypes.filter(v => v != type);
+
+    this._prefSvc.setCharPref(PREF_DISABLED_PLUGIN_TYPES,
+                              disabledPluginTypes.join(","));
+
+    // Update the category manager so existing browser windows update.
+    this._categoryMgr.
+      addCategoryEntry("Gecko-Content-Viewers",
+                       this.type,
+                       "@mozilla.org/content/plugin/document-loader-factory;1",
+                       false,
+                       true);
+  },
+
+
+  // Storage
+
+  store: function() {
+    this._handlerSvc.store(this.wrappedHandlerInfo);
+  },
+
+
+  // Icons
+
+  get smallIcon() {
+    return this._getIcon(16);
+  },
+
+  _getIcon: function(aSize) {
+    if (this.primaryExtension)
+      return "moz-icon://goat." + this.primaryExtension + "?size=" + aSize;
+
+    if (this.wrappedHandlerInfo instanceof Ci.nsIMIMEInfo)
+      return "moz-icon://goat?size=" + aSize + "&contentType=" + this.type;
+
+    // FIXME: consider returning some generic icon when we can't get a URL for
+    // one (for example in the case of protocol schemes).  Filed as bug 395141.
+    return null;
+  }
+
+};
+
+
+// Feed Handler Info
+
+/**
+ * This object implements nsIHandlerInfo for the feed types.  It's a separate
+ * object because we currently store handling information for the feed type
+ * in a set of preferences rather than the nsIHandlerService-managed datastore.
+ *
+ * This object inherits from HandlerInfoWrapper in order to get functionality
+ * that isn't special to the feed type.
+ *
+ * XXX Should we inherit from HandlerInfoWrapper?  After all, we override
+ * most of that wrapper's properties and methods, and we have to dance around
+ * the fact that the wrapper expects to have a wrappedHandlerInfo, which we
+ * don't provide.
+ */
+
+function FeedHandlerInfo(aMIMEType) {
+  HandlerInfoWrapper.call(this, aMIMEType, null);
+}
+
+FeedHandlerInfo.prototype = {
+  __proto__: HandlerInfoWrapper.prototype,
+
+  // Convenience Utils
+
+  _converterSvc:
+    Cc["@mozilla.org/embeddor.implemented/web-content-handler-registrar;1"].
+    getService(Ci.nsIWebContentConverterService),
+
+  _shellSvc: AppConstants.HAVE_SHELL_SERVICE ? getShellService() : null,
+
+  // nsIHandlerInfo
+
+  get description() {
+    return this.element("bundlePreferences").getString(this._appPrefLabel);
+  },
+
+  get preferredApplicationHandler() {
+    switch (this.element(this._prefSelectedReader).value) {
+      case "client":
+        var file = this.element(this._prefSelectedApp).value;
+        if (file)
+          return getLocalHandlerApp(file);
+
+        return null;
+
+      case "web":
+        var uri = this.element(this._prefSelectedWeb).value;
+        if (!uri)
+          return null;
+        return this._converterSvc.getWebContentHandlerByURI(this.type, uri);
+
+      case "bookmarks":
+      default:
+        // When the pref is set to bookmarks, we handle feeds internally,
+        // we don't forward them to a local or web handler app, so there is
+        // no preferred handler.
+        return null;
+    }
+  },
+
+  set preferredApplicationHandler(aNewValue) {
+    if (aNewValue instanceof Ci.nsILocalHandlerApp) {
+      this.element(this._prefSelectedApp).value = aNewValue.executable;
+      this.element(this._prefSelectedReader).value = "client";
+    }
+    else if (aNewValue instanceof Ci.nsIWebContentHandlerInfo) {
+      this.element(this._prefSelectedWeb).value = aNewValue.uri;
+      this.element(this._prefSelectedReader).value = "web";
+      // Make the web handler be the new "auto handler" for feeds.
+      // Note: we don't have to unregister the auto handler when the user picks
+      // a non-web handler (local app, Live Bookmarks, etc.) because the service
+      // only uses the "auto handler" when the selected reader is a web handler.
+      // We also don't have to unregister it when the user turns on "always ask"
+      // (i.e. preview in browser), since that also overrides the auto handler.
+      this._converterSvc.setAutoHandler(this.type, aNewValue);
+    }
+  },
+
+  _possibleApplicationHandlers: null,
+
+  get possibleApplicationHandlers() {
+    if (this._possibleApplicationHandlers)
+      return this._possibleApplicationHandlers;
+
+    // A minimal implementation of nsIMutableArray.  It only supports the two
+    // methods its callers invoke, namely appendElement and nsIArray::enumerate.
+    this._possibleApplicationHandlers = {
+      _inner: [],
+      _removed: [],
+
+      QueryInterface: function(aIID) {
+        if (aIID.equals(Ci.nsIMutableArray) ||
+            aIID.equals(Ci.nsIArray) ||
+            aIID.equals(Ci.nsISupports))
+          return this;
+
+        throw Cr.NS_ERROR_NO_INTERFACE;
+      },
+
+      get length() {
+        return this._inner.length;
+      },
+
+      enumerate: function() {
+        return new ArrayEnumerator(this._inner);
+      },
+
+      appendElement: function(aHandlerApp, aWeak) {
+        this._inner.push(aHandlerApp);
+      },
+
+      removeElementAt: function(aIndex) {
+        this._removed.push(this._inner[aIndex]);
+        this._inner.splice(aIndex, 1);
+      },
+
+      queryElementAt: function(aIndex, aInterface) {
+        return this._inner[aIndex].QueryInterface(aInterface);
+      }
+    };
+
+    // Add the selected local app if it's different from the OS default handler.
+    // Unlike for other types, we can store only one local app at a time for the
+    // feed type, since we store it in a preference that historically stores
+    // only a single path.  But we display all the local apps the user chooses
+    // while the prefpane is open, only dropping the list when the user closes
+    // the prefpane, for maximum usability and consistency with other types.
+    var preferredAppFile = this.element(this._prefSelectedApp).value;
+    if (preferredAppFile) {
+      let preferredApp = getLocalHandlerApp(preferredAppFile);
+      let defaultApp = this._defaultApplicationHandler;
+      if (!defaultApp || !defaultApp.equals(preferredApp))
+        this._possibleApplicationHandlers.appendElement(preferredApp, false);
+    }
+
+    // Add the registered web handlers.  There can be any number of these.
+    var webHandlers = this._converterSvc.getContentHandlers(this.type);
+    for (let webHandler of webHandlers)
+      this._possibleApplicationHandlers.appendElement(webHandler, false);
+
+    return this._possibleApplicationHandlers;
+  },
+
+  __defaultApplicationHandler: undefined,
+  get _defaultApplicationHandler() {
+    if (typeof this.__defaultApplicationHandler != "undefined")
+      return this.__defaultApplicationHandler;
+
+    var defaultFeedReader = null;
+    if (AppConstants.HAVE_SHELL_SERVICE) {
+      try {
+        defaultFeedReader = this._shellSvc.defaultFeedReader;
+      }
+      catch (ex) {
+        // no default reader or _shellSvc is null
+      }
+    }
+
+    if (defaultFeedReader) {
+      let handlerApp = Cc["@mozilla.org/uriloader/local-handler-app;1"].
+                       createInstance(Ci.nsIHandlerApp);
+      handlerApp.name = getFileDisplayName(defaultFeedReader);
+      handlerApp.QueryInterface(Ci.nsILocalHandlerApp);
+      handlerApp.executable = defaultFeedReader;
+
+      this.__defaultApplicationHandler = handlerApp;
+    }
+    else {
+      this.__defaultApplicationHandler = null;
+    }
+
+    return this.__defaultApplicationHandler;
+  },
+
+  get hasDefaultHandler() {
+    if (AppConstants.HAVE_SHELL_SERVICE) {
+      try {
+        if (this._shellSvc.defaultFeedReader)
+          return true;
+      }
+      catch (ex) {
+        // no default reader or _shellSvc is null
+      }
+    }
+
+    return false;
+  },
+
+  get defaultDescription() {
+    if (this.hasDefaultHandler)
+      return this._defaultApplicationHandler.name;
+
+    // Should we instead return null?
+    return "";
+  },
+
+  // What to do with content of this type.
+  get preferredAction() {
+    switch (this.element(this._prefSelectedAction).value) {
+
+      case "bookmarks":
+        return Ci.nsIHandlerInfo.handleInternally;
+
+      case "reader": {
+        let preferredApp = this.preferredApplicationHandler;
+        let defaultApp = this._defaultApplicationHandler;
+
+        // If we have a valid preferred app, return useSystemDefault if it's
+        // the default app; otherwise return useHelperApp.
+        if (gApplicationsPane.isValidHandlerApp(preferredApp)) {
+          if (defaultApp && defaultApp.equals(preferredApp))
+            return Ci.nsIHandlerInfo.useSystemDefault;
+
+          return Ci.nsIHandlerInfo.useHelperApp;
+        }
+
+        // The pref is set to "reader", but we don't have a valid preferred app.
+        // What do we do now?  Not sure this is the best option (perhaps we
+        // should direct the user to the default app, if any), but for now let's
+        // direct the user to live bookmarks.
+        return Ci.nsIHandlerInfo.handleInternally;
+      }
+
+      // If the action is "ask", then alwaysAskBeforeHandling will override
+      // the action, so it doesn't matter what we say it is, it just has to be
+      // something that doesn't cause the controller to hide the type.
+      case "ask":
+      default:
+        return Ci.nsIHandlerInfo.handleInternally;
+    }
+  },
+
+  set preferredAction(aNewValue) {
+    switch (aNewValue) {
+
+      case Ci.nsIHandlerInfo.handleInternally:
+        this.element(this._prefSelectedReader).value = "bookmarks";
+        break;
+
+      case Ci.nsIHandlerInfo.useHelperApp:
+        this.element(this._prefSelectedAction).value = "reader";
+        // The controller has already set preferredApplicationHandler
+        // to the new helper app.
+        break;
+
+      case Ci.nsIHandlerInfo.useSystemDefault:
+        this.element(this._prefSelectedAction).value = "reader";
+        this.preferredApplicationHandler = this._defaultApplicationHandler;
+        break;
+    }
+  },
+
+  get alwaysAskBeforeHandling() {
+    return this.element(this._prefSelectedAction).value == "ask";
+  },
+
+  set alwaysAskBeforeHandling(aNewValue) {
+    if (aNewValue == true)
+      this.element(this._prefSelectedAction).value = "ask";
+    else
+      this.element(this._prefSelectedAction).value = "reader";
+  },
+
+  // Whether or not we are currently storing the action selected by the user.
+  // We use this to suppress notification-triggered updates to the list when
+  // we make changes that may spawn such updates, specifically when we change
+  // the action for the feed type, which results in feed preference updates,
+  // which spawn "pref changed" notifications that would otherwise cause us
+  // to rebuild the view unnecessarily.
+  _storingAction: false,
+
+
+  // nsIMIMEInfo
+
+  get primaryExtension() {
+    return "xml";
+  },
+
+
+  // Storage
+
+  // Changes to the preferred action and handler take effect immediately
+  // (we write them out to the preferences right as they happen),
+  // so we when the controller calls store() after modifying the handlers,
+  // the only thing we need to store is the removal of possible handlers
+  // XXX Should we hold off on making the changes until this method gets called?
+  store: function() {
+    for (let app of this._possibleApplicationHandlers._removed) {
+      if (app instanceof Ci.nsILocalHandlerApp) {
+        let pref = this.element(PREF_FEED_SELECTED_APP);
+        var preferredAppFile = pref.value;
+        if (preferredAppFile) {
+          let preferredApp = getLocalHandlerApp(preferredAppFile);
+          if (app.equals(preferredApp))
+            pref.reset();
+        }
+      }
+      else {
+        app.QueryInterface(Ci.nsIWebContentHandlerInfo);
+        this._converterSvc.removeContentHandler(app.contentType, app.uri);
+      }
+    }
+    this._possibleApplicationHandlers._removed = [];
+  },
+
+
+  // Icons
+
+  get smallIcon() {
+    return this._smallIcon;
+  }
+
+};
+
+var feedHandlerInfo = {
+  __proto__: new FeedHandlerInfo(TYPE_MAYBE_FEED),
+  _prefSelectedApp: PREF_FEED_SELECTED_APP,
+  _prefSelectedWeb: PREF_FEED_SELECTED_WEB,
+  _prefSelectedAction: PREF_FEED_SELECTED_ACTION,
+  _prefSelectedReader: PREF_FEED_SELECTED_READER,
+  _smallIcon: "chrome://browser/skin/feeds/feedIcon16.png",
+  _appPrefLabel: "webFeed"
+}
+
+var videoFeedHandlerInfo = {
+  __proto__: new FeedHandlerInfo(TYPE_MAYBE_VIDEO_FEED),
+  _prefSelectedApp: PREF_VIDEO_FEED_SELECTED_APP,
+  _prefSelectedWeb: PREF_VIDEO_FEED_SELECTED_WEB,
+  _prefSelectedAction: PREF_VIDEO_FEED_SELECTED_ACTION,
+  _prefSelectedReader: PREF_VIDEO_FEED_SELECTED_READER,
+  _smallIcon: "chrome://browser/skin/feeds/videoFeedIcon16.png",
+  _appPrefLabel: "videoPodcastFeed"
+}
+
+var audioFeedHandlerInfo = {
+  __proto__: new FeedHandlerInfo(TYPE_MAYBE_AUDIO_FEED),
+  _prefSelectedApp: PREF_AUDIO_FEED_SELECTED_APP,
+  _prefSelectedWeb: PREF_AUDIO_FEED_SELECTED_WEB,
+  _prefSelectedAction: PREF_AUDIO_FEED_SELECTED_ACTION,
+  _prefSelectedReader: PREF_AUDIO_FEED_SELECTED_READER,
+  _smallIcon: "chrome://browser/skin/feeds/audioFeedIcon16.png",
+  _appPrefLabel: "audioPodcastFeed"
+}
+
+/**
+ * InternalHandlerInfoWrapper provides a basic mechanism to create an internal
+ * mime type handler that can be enabled/disabled in the applications preference
+ * menu.
+ */
+function InternalHandlerInfoWrapper(aMIMEType) {
+  var mimeSvc = Cc["@mozilla.org/mime;1"].getService(Ci.nsIMIMEService);
+  var handlerInfo = mimeSvc.getFromTypeAndExtension(aMIMEType, null);
+
+  HandlerInfoWrapper.call(this, aMIMEType, handlerInfo);
+}
+
+InternalHandlerInfoWrapper.prototype = {
+  __proto__: HandlerInfoWrapper.prototype,
+
+  // Override store so we so we can notify any code listening for registration
+  // or unregistration of this handler.
+  store: function() {
+    HandlerInfoWrapper.prototype.store.call(this);
+    Services.obs.notifyObservers(null, this._handlerChanged, null);
+  },
+
+  get enabled() {
+    throw Cr.NS_ERROR_NOT_IMPLEMENTED;
+  },
+
+  get description() {
+    return this.element("bundlePreferences").getString(this._appPrefLabel);
+  }
+};
+
+var pdfHandlerInfo = {
+  __proto__: new InternalHandlerInfoWrapper(TYPE_PDF),
+  _handlerChanged: TOPIC_PDFJS_HANDLER_CHANGED,
+  _appPrefLabel: "portableDocumentFormat",
+  get enabled() {
+    return !Services.prefs.getBoolPref(PREF_PDFJS_DISABLED);
+  },
+};
+
+
+// Prefpane Controller
+
+var gApplicationsPane = {
+  // The set of types the app knows how to handle.  A hash of HandlerInfoWrapper
+  // objects, indexed by type.
+  _handledTypes: {},
+
+  // The list of types we can show, sorted by the sort column/direction.
+  // An array of HandlerInfoWrapper objects.  We build this list when we first
+  // load the data and then rebuild it when users change a pref that affects
+  // what types we can show or change the sort column/direction.
+  // Note: this isn't necessarily the list of types we *will* show; if the user
+  // provides a filter string, we'll only show the subset of types in this list
+  // that match that string.
+  _visibleTypes: [],
+
+  // A count of the number of times each visible type description appears.
+  // We use these counts to determine whether or not to annotate descriptions
+  // with their types to distinguish duplicate descriptions from each other.
+  // A hash of integer counts, indexed by string description.
+  _visibleTypeDescriptionCount: {},
+
+
+  // Convenience & Performance Shortcuts
+
+  // These get defined by init().
+  _brandShortName : null,
+  _prefsBundle    : null,
+  _list           : null,
+  _filter         : null,
+
+  _prefSvc      : Cc["@mozilla.org/preferences-service;1"].
+                  getService(Ci.nsIPrefBranch),
+
+  _mimeSvc      : Cc["@mozilla.org/mime;1"].
+                  getService(Ci.nsIMIMEService),
+
+  _helperAppSvc : Cc["@mozilla.org/uriloader/external-helper-app-service;1"].
+                  getService(Ci.nsIExternalHelperAppService),
+
+  _handlerSvc   : Cc["@mozilla.org/uriloader/handler-service;1"].
+                  getService(Ci.nsIHandlerService),
+
+  _ioSvc        : Cc["@mozilla.org/network/io-service;1"].
+                  getService(Ci.nsIIOService),
+
+
+  // Initialization & Destruction
+
+  init: function() {
+    function setEventListener(aId, aEventType, aCallback)
+    {
+      document.getElementById(aId)
+              .addEventListener(aEventType, aCallback.bind(gApplicationsPane));
+    }
+
+    // Initialize shortcuts to some commonly accessed elements & values.
+    this._brandShortName =
+      document.getElementById("bundleBrand").getString("brandShortName");
+    this._prefsBundle = document.getElementById("bundlePreferences");
+    this._list = document.getElementById("handlersView");
+    this._filter = document.getElementById("filter");
+
+    // Observe preferences that influence what we display so we can rebuild
+    // the view when they change.
+    this._prefSvc.addObserver(PREF_SHOW_PLUGINS_IN_LIST, this, false);
+    this._prefSvc.addObserver(PREF_HIDE_PLUGINS_WITHOUT_EXTENSIONS, this, false);
+    this._prefSvc.addObserver(PREF_FEED_SELECTED_APP, this, false);
+    this._prefSvc.addObserver(PREF_FEED_SELECTED_WEB, this, false);
+    this._prefSvc.addObserver(PREF_FEED_SELECTED_ACTION, this, false);
+    this._prefSvc.addObserver(PREF_FEED_SELECTED_READER, this, false);
+
+    this._prefSvc.addObserver(PREF_VIDEO_FEED_SELECTED_APP, this, false);
+    this._prefSvc.addObserver(PREF_VIDEO_FEED_SELECTED_WEB, this, false);
+    this._prefSvc.addObserver(PREF_VIDEO_FEED_SELECTED_ACTION, this, false);
+    this._prefSvc.addObserver(PREF_VIDEO_FEED_SELECTED_READER, this, false);
+
+    this._prefSvc.addObserver(PREF_AUDIO_FEED_SELECTED_APP, this, false);
+    this._prefSvc.addObserver(PREF_AUDIO_FEED_SELECTED_WEB, this, false);
+    this._prefSvc.addObserver(PREF_AUDIO_FEED_SELECTED_ACTION, this, false);
+    this._prefSvc.addObserver(PREF_AUDIO_FEED_SELECTED_READER, this, false);
+
+
+    setEventListener("focusSearch1", "command", gApplicationsPane.focusFilterBox);
+    setEventListener("focusSearch2", "command", gApplicationsPane.focusFilterBox);
+    setEventListener("filter", "command", gApplicationsPane.filter);
+    setEventListener("handlersView", "select",
+      gApplicationsPane.onSelectionChanged);
+    setEventListener("typeColumn", "click", gApplicationsPane.sort);
+    setEventListener("actionColumn", "click", gApplicationsPane.sort);
+
+    // Listen for window unload so we can remove our preference observers.
+    window.addEventListener("unload", this, false);
+
+    // Figure out how we should be sorting the list.  We persist sort settings
+    // across sessions, so we can't assume the default sort column/direction.
+    // XXX should we be using the XUL sort service instead?
+    if (document.getElementById("actionColumn").hasAttribute("sortDirection")) {
+      this._sortColumn = document.getElementById("actionColumn");
+      // The typeColumn element always has a sortDirection attribute,
+      // either because it was persisted or because the default value
+      // from the xul file was used.  If we are sorting on the other
+      // column, we should remove it.
+      document.getElementById("typeColumn").removeAttribute("sortDirection");
+    }
+    else
+      this._sortColumn = document.getElementById("typeColumn");
+
+    // Load the data and build the list of handlers.
+    // By doing this in a timeout, we let the preferences dialog resize itself
+    // to an appropriate size before we add a bunch of items to the list.
+    // Otherwise, if there are many items, and the Applications prefpane
+    // is the one that gets displayed when the user first opens the dialog,
+    // the dialog might stretch too much in an attempt to fit them all in.
+    // XXX Shouldn't we perhaps just set a max-height on the richlistbox?
+    var _delayedPaneLoad = function(self) {
+      self._loadData();
+      self._rebuildVisibleTypes();
+      self._sortVisibleTypes();
+      self._rebuildView();
+
+      // Notify observers that the UI is now ready
+      Cc["@mozilla.org/observer-service;1"].getService(Ci.nsIObserverService).
+      notifyObservers(window, "app-handler-pane-loaded", null);
+    }
+    setTimeout(_delayedPaneLoad, 0, this);
+  },
+
+  destroy: function() {
+    window.removeEventListener("unload", this, false);
+    this._prefSvc.removeObserver(PREF_SHOW_PLUGINS_IN_LIST, this);
+    this._prefSvc.removeObserver(PREF_HIDE_PLUGINS_WITHOUT_EXTENSIONS, this);
+    this._prefSvc.removeObserver(PREF_FEED_SELECTED_APP, this);
+    this._prefSvc.removeObserver(PREF_FEED_SELECTED_WEB, this);
+    this._prefSvc.removeObserver(PREF_FEED_SELECTED_ACTION, this);
+    this._prefSvc.removeObserver(PREF_FEED_SELECTED_READER, this);
+
+    this._prefSvc.removeObserver(PREF_VIDEO_FEED_SELECTED_APP, this);
+    this._prefSvc.removeObserver(PREF_VIDEO_FEED_SELECTED_WEB, this);
+    this._prefSvc.removeObserver(PREF_VIDEO_FEED_SELECTED_ACTION, this);
+    this._prefSvc.removeObserver(PREF_VIDEO_FEED_SELECTED_READER, this);
+
+    this._prefSvc.removeObserver(PREF_AUDIO_FEED_SELECTED_APP, this);
+    this._prefSvc.removeObserver(PREF_AUDIO_FEED_SELECTED_WEB, this);
+    this._prefSvc.removeObserver(PREF_AUDIO_FEED_SELECTED_ACTION, this);
+    this._prefSvc.removeObserver(PREF_AUDIO_FEED_SELECTED_READER, this);
+  },
+
+
+  // nsISupports
+
+  QueryInterface: function(aIID) {
+    if (aIID.equals(Ci.nsIObserver) ||
+        aIID.equals(Ci.nsIDOMEventListener ||
+        aIID.equals(Ci.nsISupports)))
+      return this;
+
+    throw Cr.NS_ERROR_NO_INTERFACE;
+  },
+
+
+  // nsIObserver
+
+  observe: function (aSubject, aTopic, aData) {
+    // Rebuild the list when there are changes to preferences that influence
+    // whether or not to show certain entries in the list.
+    if (aTopic == "nsPref:changed" && !this._storingAction) {
+      // These two prefs alter the list of visible types, so we have to rebuild
+      // that list when they change.
+      if (aData == PREF_SHOW_PLUGINS_IN_LIST ||
+          aData == PREF_HIDE_PLUGINS_WITHOUT_EXTENSIONS) {
+        this._rebuildVisibleTypes();
+        this._sortVisibleTypes();
+      }
+
+      // All the prefs we observe can affect what we display, so we rebuild
+      // the view when any of them changes.
+      this._rebuildView();
+    }
+  },
+
+
+  // nsIDOMEventListener
+
+  handleEvent: function(aEvent) {
+    if (aEvent.type == "unload") {
+      this.destroy();
+    }
+  },
+
+
+  // Composed Model Construction
+
+  _loadData: function() {
+    this._loadFeedHandler();
+    this._loadInternalHandlers();
+    this._loadPluginHandlers();
+    this._loadApplicationHandlers();
+  },
+
+  _loadFeedHandler: function() {
+    this._handledTypes[TYPE_MAYBE_FEED] = feedHandlerInfo;
+    feedHandlerInfo.handledOnlyByPlugin = false;
+
+    this._handledTypes[TYPE_MAYBE_VIDEO_FEED] = videoFeedHandlerInfo;
+    videoFeedHandlerInfo.handledOnlyByPlugin = false;
+
+    this._handledTypes[TYPE_MAYBE_AUDIO_FEED] = audioFeedHandlerInfo;
+    audioFeedHandlerInfo.handledOnlyByPlugin = false;
+  },
+
+  /**
+   * Load higher level internal handlers so they can be turned on/off in the
+   * applications menu.
+   */
+  _loadInternalHandlers: function() {
+    var internalHandlers = [pdfHandlerInfo];
+    for (let internalHandler of internalHandlers) {
+      if (internalHandler.enabled) {
+        this._handledTypes[internalHandler.type] = internalHandler;
+      }
+    }
+  },
+
+  /**
+   * Load the set of handlers defined by plugins.
+   *
+   * Note: if there's more than one plugin for a given MIME type, we assume
+   * the last one is the one that the application will use.  That may not be
+   * correct, but it's how we've been doing it for years.
+   *
+   * Perhaps we should instead query navigator.mimeTypes for the set of types
+   * supported by the application and then get the plugin from each MIME type's
+   * enabledPlugin property.  But if there's a plugin for a type, we need
+   * to know about it even if it isn't enabled, since we're going to give
+   * the user an option to enable it.
+   *
+   * Also note that enabledPlugin does not get updated when
+   * plugin.disable_full_page_plugin_for_types changes, so even if we could use
+   * enabledPlugin to get the plugin that would be used, we'd still need to
+   * check the pref ourselves to find out if it's enabled.
+   */
+  _loadPluginHandlers: function() {
+    "use strict";
+
+    let mimeTypes = navigator.mimeTypes;
+
+    for (let mimeType of mimeTypes) {
+      let handlerInfoWrapper;
+      if (mimeType.type in this._handledTypes) {
+        handlerInfoWrapper = this._handledTypes[mimeType.type];
+      } else {
+        let wrappedHandlerInfo =
+              this._mimeSvc.getFromTypeAndExtension(mimeType.type, null);
+        handlerInfoWrapper = new HandlerInfoWrapper(mimeType.type, wrappedHandlerInfo);
+        handlerInfoWrapper.handledOnlyByPlugin = true;
+        this._handledTypes[mimeType.type] = handlerInfoWrapper;
+      }
+      handlerInfoWrapper.pluginName = mimeType.enabledPlugin.name;
+    }
+  },
+
+  /**
+   * Load the set of handlers defined by the application datastore.
+   */
+  _loadApplicationHandlers: function() {
+    var wrappedHandlerInfos = this._handlerSvc.enumerate();
+    while (wrappedHandlerInfos.hasMoreElements()) {
+      let wrappedHandlerInfo =
+        wrappedHandlerInfos.getNext().QueryInterface(Ci.nsIHandlerInfo);
+      let type = wrappedHandlerInfo.type;
+
+      let handlerInfoWrapper;
+      if (type in this._handledTypes)
+        handlerInfoWrapper = this._handledTypes[type];
+      else {
+        handlerInfoWrapper = new HandlerInfoWrapper(type, wrappedHandlerInfo);
+        this._handledTypes[type] = handlerInfoWrapper;
+      }
+
+      handlerInfoWrapper.handledOnlyByPlugin = false;
+    }
+  },
+
+
+  // View Construction
+
+  _rebuildVisibleTypes: function() {
+    // Reset the list of visible types and the visible type description counts.
+    this._visibleTypes = [];
+    this._visibleTypeDescriptionCount = {};
+
+    // Get the preferences that help determine what types to show.
+    var showPlugins = this._prefSvc.getBoolPref(PREF_SHOW_PLUGINS_IN_LIST);
+    var hidePluginsWithoutExtensions =
+      this._prefSvc.getBoolPref(PREF_HIDE_PLUGINS_WITHOUT_EXTENSIONS);
+
+    for (let type in this._handledTypes) {
+      let handlerInfo = this._handledTypes[type];
+
+      // Hide plugins without associated extensions if so prefed so we don't
+      // show a whole bunch of obscure types handled by plugins on Mac.
+      // Note: though protocol types don't have extensions, we still show them;
+      // the pref is only meant to be applied to MIME types, since plugins are
+      // only associated with MIME types.
+      // FIXME: should we also check the "suffixes" property of the plugin?
+      // Filed as bug 395135.
+      if (hidePluginsWithoutExtensions && handlerInfo.handledOnlyByPlugin &&
+          handlerInfo.wrappedHandlerInfo instanceof Ci.nsIMIMEInfo &&
+          !handlerInfo.primaryExtension)
+        continue;
+
+      // Hide types handled only by plugins if so prefed.
+      if (handlerInfo.handledOnlyByPlugin && !showPlugins)
+        continue;
+
+      // We couldn't find any reason to exclude the type, so include it.
+      this._visibleTypes.push(handlerInfo);
+
+      if (handlerInfo.description in this._visibleTypeDescriptionCount)
+        this._visibleTypeDescriptionCount[handlerInfo.description]++;
+      else
+        this._visibleTypeDescriptionCount[handlerInfo.description] = 1;
+    }
+  },
+
+  _rebuildView: function() {
+    // Clear the list of entries.
+    while (this._list.childNodes.length > 1)
+      this._list.removeChild(this._list.lastChild);
+
+    var visibleTypes = this._visibleTypes;
+
+    // If the user is filtering the list, then only show matching types.
+    if (this._filter.value)
+      visibleTypes = visibleTypes.filter(this._matchesFilter, this);
+
+    for (let visibleType of visibleTypes) {
+      let item = document.createElement("richlistitem");
+      item.setAttribute("type", visibleType.type);
+      item.setAttribute("typeDescription", this._describeType(visibleType));
+      if (visibleType.smallIcon)
+        item.setAttribute("typeIcon", visibleType.smallIcon);
+      item.setAttribute("actionDescription",
+                        this._describePreferredAction(visibleType));
+
+      if (!this._setIconClassForPreferredAction(visibleType, item)) {
+        item.setAttribute("actionIcon",
+                          this._getIconURLForPreferredAction(visibleType));
+      }
+
+      this._list.appendChild(item);
+    }
+
+    this._selectLastSelectedType();
+  },
+
+  _matchesFilter: function(aType) {
+    var filterValue = this._filter.value.toLowerCase();
+    return this._describeType(aType).toLowerCase().indexOf(filterValue) != -1 ||
+           this._describePreferredAction(aType).toLowerCase().indexOf(filterValue) != -1;
+  },
+
+  /**
+   * Describe, in a human-readable fashion, the type represented by the given
+   * handler info object.  Normally this is just the description provided by
+   * the info object, but if more than one object presents the same description,
+   * then we annotate the duplicate descriptions with the type itself to help
+   * users distinguish between those types.
+   *
+   * @param aHandlerInfo {nsIHandlerInfo} the type being described
+   * @returns {string} a description of the type
+   */
+  _describeType: function(aHandlerInfo) {
+    if (this._visibleTypeDescriptionCount[aHandlerInfo.description] > 1)
+      return this._prefsBundle.getFormattedString("typeDescriptionWithType",
+                                                  [aHandlerInfo.description,
+                                                   aHandlerInfo.type]);
+
+    return aHandlerInfo.description;
+  },
+
+  /**
+   * Describe, in a human-readable fashion, the preferred action to take on
+   * the type represented by the given handler info object.
+   *
+   * XXX Should this be part of the HandlerInfoWrapper interface?  It would
+   * violate the separation of model and view, but it might make more sense
+   * nonetheless (f.e. it would make sortTypes easier).
+   *
+   * @param aHandlerInfo {nsIHandlerInfo} the type whose preferred action
+   *                                      is being described
+   * @returns {string} a description of the action
+   */
+  _describePreferredAction: function(aHandlerInfo) {
+    // alwaysAskBeforeHandling overrides the preferred action, so if that flag
+    // is set, then describe that behavior instead.  For most types, this is
+    // the "alwaysAsk" string, but for the feed type we show something special.
+    if (aHandlerInfo.alwaysAskBeforeHandling) {
+      if (isFeedType(aHandlerInfo.type))
+        return this._prefsBundle.getFormattedString("previewInApp",
+                                                    [this._brandShortName]);
+      return this._prefsBundle.getString("alwaysAsk");
+    }
+
+    switch (aHandlerInfo.preferredAction) {
+      case Ci.nsIHandlerInfo.saveToDisk:
+        return this._prefsBundle.getString("saveFile");
+
+      case Ci.nsIHandlerInfo.useHelperApp:
+        var preferredApp = aHandlerInfo.preferredApplicationHandler;
+        var name;
+        if (preferredApp instanceof Ci.nsILocalHandlerApp)
+          name = getFileDisplayName(preferredApp.executable);
+        else
+          name = preferredApp.name;
+        return this._prefsBundle.getFormattedString("useApp", [name]);
+
+      case Ci.nsIHandlerInfo.handleInternally:
+        // For the feed type, handleInternally means live bookmarks.
+        if (isFeedType(aHandlerInfo.type)) {
+          return this._prefsBundle.getFormattedString("addLiveBookmarksInApp",
+                                                      [this._brandShortName]);
+        }
+
+        if (aHandlerInfo instanceof InternalHandlerInfoWrapper) {
+          return this._prefsBundle.getFormattedString("previewInApp",
+                                                      [this._brandShortName]);
+        }
+
+        // For other types, handleInternally looks like either useHelperApp
+        // or useSystemDefault depending on whether or not there's a preferred
+        // handler app.
+        if (this.isValidHandlerApp(aHandlerInfo.preferredApplicationHandler))
+          return aHandlerInfo.preferredApplicationHandler.name;
+
+        return aHandlerInfo.defaultDescription;
+
+        // XXX Why don't we say the app will handle the type internally?
+        // Is it because the app can't actually do that?  But if that's true,
+        // then why would a preferredAction ever get set to this value
+        // in the first place?
+
+      case Ci.nsIHandlerInfo.useSystemDefault:
+        return this._prefsBundle.getFormattedString("useDefault",
+                                                    [aHandlerInfo.defaultDescription]);
+
+      case kActionUsePlugin:
+        return this._prefsBundle.getFormattedString("usePluginIn",
+                                                    [aHandlerInfo.pluginName,
+                                                     this._brandShortName]);
+      default:
+        throw new Error(`Unexpected preferredAction: ${aHandlerInfo.preferredAction}`);
+    }
+  },
+
+  _selectLastSelectedType: function() {
+    // If the list is disabled by the pref.downloads.disable_button.edit_actions
+    // preference being locked, then don't select the type, as that would cause
+    // it to appear selected, with a different background and an actions menu
+    // that makes it seem like you can choose an action for the type.
+    if (this._list.disabled)
+      return;
+
+    var lastSelectedType = this._list.getAttribute("lastSelectedType");
+    if (!lastSelectedType)
+      return;
+
+    var item = this._list.getElementsByAttribute("type", lastSelectedType)[0];
+    if (!item)
+      return;
+
+    this._list.selectedItem = item;
+  },
+
+  /**
+   * Whether or not the given handler app is valid.
+   *
+   * @param aHandlerApp {nsIHandlerApp} the handler app in question
+   *
+   * @returns {boolean} whether or not it's valid
+   */
+  isValidHandlerApp: function(aHandlerApp) {
+    if (!aHandlerApp)
+      return false;
+
+    if (aHandlerApp instanceof Ci.nsILocalHandlerApp)
+      return this._isValidHandlerExecutable(aHandlerApp.executable);
+
+    if (aHandlerApp instanceof Ci.nsIWebHandlerApp)
+      return aHandlerApp.uriTemplate;
+
+    if (aHandlerApp instanceof Ci.nsIWebContentHandlerInfo)
+      return aHandlerApp.uri;
+
+    return false;
+  },
+
+  _isValidHandlerExecutable: function(aExecutable) {
+    let leafName;
+    if (AppConstants.platform == "win") {
+      leafName = `${AppConstants.MOZ_APP_NAME}.exe`;
+    } else if (AppConstants.platform == "macosx") {
+      leafName = AppConstants.MOZ_MACBUNDLE_NAME;
+    } else {
+      leafName = `${AppConstants.MOZ_APP_NAME}-bin`;
+    }
+    return aExecutable &&
+           aExecutable.exists() &&
+           aExecutable.isExecutable() &&
+// XXXben - we need to compare this with the running instance executable
+//          just don't know how to do that via script...
+// XXXmano TBD: can probably add this to nsIShellService
+           aExecutable.leafName != leafName;
+  },
+
+  /**
+   * Rebuild the actions menu for the selected entry.  Gets called by
+   * the richlistitem constructor when an entry in the list gets selected.
+   */
+  rebuildActionsMenu: function() {
+    var typeItem = this._list.selectedItem;
+    var handlerInfo = this._handledTypes[typeItem.type];
+    var menu =
+      document.getAnonymousElementByAttribute(typeItem, "class", "actionsMenu");
+    var menuPopup = menu.menupopup;
+
+    // Clear out existing items.
+    while (menuPopup.hasChildNodes())
+      menuPopup.removeChild(menuPopup.lastChild);
+
+    // Add the "Preview in Firefox" option for optional internal handlers.
+    if (handlerInfo instanceof InternalHandlerInfoWrapper) {
+      let internalMenuItem = document.createElement("menuitem");
+      internalMenuItem.setAttribute("action", Ci.nsIHandlerInfo.handleInternally);
+      let label = this._prefsBundle.getFormattedString("previewInApp",
+                                                       [this._brandShortName]);
+      internalMenuItem.setAttribute("label", label);
+      internalMenuItem.setAttribute("tooltiptext", label);
+      internalMenuItem.setAttribute(APP_ICON_ATTR_NAME, "ask");
+      menuPopup.appendChild(internalMenuItem);
+    }
+
+    {
+      var askMenuItem = document.createElement("menuitem");
+      askMenuItem.setAttribute("action", Ci.nsIHandlerInfo.alwaysAsk);
+      let label;
+      if (isFeedType(handlerInfo.type))
+        label = this._prefsBundle.getFormattedString("previewInApp",
+                                                     [this._brandShortName]);
+      else
+        label = this._prefsBundle.getString("alwaysAsk");
+      askMenuItem.setAttribute("label", label);
+      askMenuItem.setAttribute("tooltiptext", label);
+      askMenuItem.setAttribute(APP_ICON_ATTR_NAME, "ask");
+      menuPopup.appendChild(askMenuItem);
+    }
+
+    // Create a menu item for saving to disk.
+    // Note: this option isn't available to protocol types, since we don't know
+    // what it means to save a URL having a certain scheme to disk, nor is it
+    // available to feeds, since the feed code doesn't implement the capability.
+    if ((handlerInfo.wrappedHandlerInfo instanceof Ci.nsIMIMEInfo) &&
+        !isFeedType(handlerInfo.type)) {
+      var saveMenuItem = document.createElement("menuitem");
+      saveMenuItem.setAttribute("action", Ci.nsIHandlerInfo.saveToDisk);
+      let label = this._prefsBundle.getString("saveFile");
+      saveMenuItem.setAttribute("label", label);
+      saveMenuItem.setAttribute("tooltiptext", label);
+      saveMenuItem.setAttribute(APP_ICON_ATTR_NAME, "save");
+      menuPopup.appendChild(saveMenuItem);
+    }
+
+    // If this is the feed type, add a Live Bookmarks item.
+    if (isFeedType(handlerInfo.type)) {
+      let internalMenuItem = document.createElement("menuitem");
+      internalMenuItem.setAttribute("action", Ci.nsIHandlerInfo.handleInternally);
+      let label = this._prefsBundle.getFormattedString("addLiveBookmarksInApp",
+                                                       [this._brandShortName]);
+      internalMenuItem.setAttribute("label", label);
+      internalMenuItem.setAttribute("tooltiptext", label);
+      internalMenuItem.setAttribute(APP_ICON_ATTR_NAME, "feed");
+      menuPopup.appendChild(internalMenuItem);
+    }
+
+    // Add a separator to distinguish these items from the helper app items
+    // that follow them.
+    let menuItem = document.createElement("menuseparator");
+    menuPopup.appendChild(menuItem);
+
+    // Create a menu item for the OS default application, if any.
+    if (handlerInfo.hasDefaultHandler) {
+      var defaultMenuItem = document.createElement("menuitem");
+      defaultMenuItem.setAttribute("action", Ci.nsIHandlerInfo.useSystemDefault);
+      let label = this._prefsBundle.getFormattedString("useDefault",
+                                                       [handlerInfo.defaultDescription]);
+      defaultMenuItem.setAttribute("label", label);
+      defaultMenuItem.setAttribute("tooltiptext", handlerInfo.defaultDescription);
+      defaultMenuItem.setAttribute("image", this._getIconURLForSystemDefault(handlerInfo));
+
+      menuPopup.appendChild(defaultMenuItem);
+    }
+
+    // Create menu items for possible handlers.
+    let preferredApp = handlerInfo.preferredApplicationHandler;
+    let possibleApps = handlerInfo.possibleApplicationHandlers.enumerate();
+    var possibleAppMenuItems = [];
+    while (possibleApps.hasMoreElements()) {
+      let possibleApp = possibleApps.getNext();
+      if (!this.isValidHandlerApp(possibleApp))
+        continue;
+
+      let menuItem = document.createElement("menuitem");
+      menuItem.setAttribute("action", Ci.nsIHandlerInfo.useHelperApp);
+      let label;
+      if (possibleApp instanceof Ci.nsILocalHandlerApp)
+        label = getFileDisplayName(possibleApp.executable);
+      else
+        label = possibleApp.name;
+      label = this._prefsBundle.getFormattedString("useApp", [label]);
+      menuItem.setAttribute("label", label);
+      menuItem.setAttribute("tooltiptext", label);
+      menuItem.setAttribute("image", this._getIconURLForHandlerApp(possibleApp));
+
+      // Attach the handler app object to the menu item so we can use it
+      // to make changes to the datastore when the user selects the item.
+      menuItem.handlerApp = possibleApp;
+
+      menuPopup.appendChild(menuItem);
+      possibleAppMenuItems.push(menuItem);
+    }
+
+    // Create a menu item for the plugin.
+    if (handlerInfo.pluginName) {
+      var pluginMenuItem = document.createElement("menuitem");
+      pluginMenuItem.setAttribute("action", kActionUsePlugin);
+      let label = this._prefsBundle.getFormattedString("usePluginIn",
+                                                       [handlerInfo.pluginName,
+                                                        this._brandShortName]);
+      pluginMenuItem.setAttribute("label", label);
+      pluginMenuItem.setAttribute("tooltiptext", label);
+      pluginMenuItem.setAttribute(APP_ICON_ATTR_NAME, "plugin");
+      menuPopup.appendChild(pluginMenuItem);
+    }
+
+    // Create a menu item for selecting a local application.
+    let canOpenWithOtherApp = true;
+    if (AppConstants.platform == "win") {
+      // On Windows, selecting an application to open another application
+      // would be meaningless so we special case executables.
+      let executableType = Cc["@mozilla.org/mime;1"].getService(Ci.nsIMIMEService)
+                                                    .getTypeFromExtension("exe");
+      canOpenWithOtherApp = handlerInfo.type != executableType;
+    }
+    if (canOpenWithOtherApp)
+    {
+      let menuItem = document.createElement("menuitem");
+      menuItem.className = "choose-app-item";
+      menuItem.addEventListener("command", function(e) {
+        gApplicationsPane.chooseApp(e);
+      });
+      let label = this._prefsBundle.getString("useOtherApp");
+      menuItem.setAttribute("label", label);
+      menuItem.setAttribute("tooltiptext", label);
+      menuPopup.appendChild(menuItem);
+    }
+
+    // Create a menu item for managing applications.
+    if (possibleAppMenuItems.length) {
+      let menuItem = document.createElement("menuseparator");
+      menuPopup.appendChild(menuItem);
+      menuItem = document.createElement("menuitem");
+      menuItem.className = "manage-app-item";
+      menuItem.addEventListener("command", function(e) {
+        gApplicationsPane.manageApp(e);
+      });
+      menuItem.setAttribute("label", this._prefsBundle.getString("manageApp"));
+      menuPopup.appendChild(menuItem);
+    }
+
+    // Select the item corresponding to the preferred action.  If the always
+    // ask flag is set, it overrides the preferred action.  Otherwise we pick
+    // the item identified by the preferred action (when the preferred action
+    // is to use a helper app, we have to pick the specific helper app item).
+    if (handlerInfo.alwaysAskBeforeHandling)
+      menu.selectedItem = askMenuItem;
+    else switch (handlerInfo.preferredAction) {
+      case Ci.nsIHandlerInfo.handleInternally:
+        menu.selectedItem = internalMenuItem;
+        break;
+      case Ci.nsIHandlerInfo.useSystemDefault:
+        menu.selectedItem = defaultMenuItem;
+        break;
+      case Ci.nsIHandlerInfo.useHelperApp:
+        if (preferredApp)
+          menu.selectedItem =
+            possibleAppMenuItems.filter(v => v.handlerApp.equals(preferredApp))[0];
+        break;
+      case kActionUsePlugin:
+        menu.selectedItem = pluginMenuItem;
+        break;
+      case Ci.nsIHandlerInfo.saveToDisk:
+        menu.selectedItem = saveMenuItem;
+        break;
+    }
+  },
+
+
+  // Sorting & Filtering
+
+  _sortColumn: null,
+
+  /**
+   * Sort the list when the user clicks on a column header.
+   */
+  sort: function (event) {
+    var column = event.target;
+
+    // If the user clicked on a new sort column, remove the direction indicator
+    // from the old column.
+    if (this._sortColumn && this._sortColumn != column)
+      this._sortColumn.removeAttribute("sortDirection");
+
+    this._sortColumn = column;
+
+    // Set (or switch) the sort direction indicator.
+    if (column.getAttribute("sortDirection") == "ascending")
+      column.setAttribute("sortDirection", "descending");
+    else
+      column.setAttribute("sortDirection", "ascending");
+
+    this._sortVisibleTypes();
+    this._rebuildView();
+  },
+
+  /**
+   * Sort the list of visible types by the current sort column/direction.
+   */
+  _sortVisibleTypes: function() {
+    if (!this._sortColumn)
+      return;
+
+    var t = this;
+
+    function sortByType(a, b) {
+      return t._describeType(a).toLowerCase().
+             localeCompare(t._describeType(b).toLowerCase());
+    }
+
+    function sortByAction(a, b) {
+      return t._describePreferredAction(a).toLowerCase().
+             localeCompare(t._describePreferredAction(b).toLowerCase());
+    }
+
+    switch (this._sortColumn.getAttribute("value")) {
+      case "type":
+        this._visibleTypes.sort(sortByType);
+        break;
+      case "action":
+        this._visibleTypes.sort(sortByAction);
+        break;
+    }
+
+    if (this._sortColumn.getAttribute("sortDirection") == "descending")
+      this._visibleTypes.reverse();
+  },
+
+  /**
+   * Filter the list when the user enters a filter term into the filter field.
+   */
+  filter: function() {
+    this._rebuildView();
+  },
+
+  focusFilterBox: function() {
+    this._filter.focus();
+    this._filter.select();
+  },
+
+
+  // Changes
+
+  onSelectAction: function(aActionItem) {
+    this._storingAction = true;
+
+    try {
+      this._storeAction(aActionItem);
+    }
+    finally {
+      this._storingAction = false;
+    }
+  },
+
+  _storeAction: function(aActionItem) {
+    var typeItem = this._list.selectedItem;
+    var handlerInfo = this._handledTypes[typeItem.type];
+
+    let action = parseInt(aActionItem.getAttribute("action"));
+
+    // Set the plugin state if we're enabling or disabling a plugin.
+    if (action == kActionUsePlugin)
+      handlerInfo.enablePluginType();
+    else if (handlerInfo.pluginName && !handlerInfo.isDisabledPluginType)
+      handlerInfo.disablePluginType();
+
+    // Set the preferred application handler.
+    // We leave the existing preferred app in the list when we set
+    // the preferred action to something other than useHelperApp so that
+    // legacy datastores that don't have the preferred app in the list
+    // of possible apps still include the preferred app in the list of apps
+    // the user can choose to handle the type.
+    if (action == Ci.nsIHandlerInfo.useHelperApp)
+      handlerInfo.preferredApplicationHandler = aActionItem.handlerApp;
+
+    // Set the "always ask" flag.
+    if (action == Ci.nsIHandlerInfo.alwaysAsk)
+      handlerInfo.alwaysAskBeforeHandling = true;
+    else
+      handlerInfo.alwaysAskBeforeHandling = false;
+
+    // Set the preferred action.
+    handlerInfo.preferredAction = action;
+
+    handlerInfo.store();
+
+    // Make sure the handler info object is flagged to indicate that there is
+    // now some user configuration for the type.
+    handlerInfo.handledOnlyByPlugin = false;
+
+    // Update the action label and image to reflect the new preferred action.
+    typeItem.setAttribute("actionDescription",
+                          this._describePreferredAction(handlerInfo));
+    if (!this._setIconClassForPreferredAction(handlerInfo, typeItem)) {
+      typeItem.setAttribute("actionIcon",
+                            this._getIconURLForPreferredAction(handlerInfo));
+    }
+  },
+
+  manageApp: function(aEvent) {
+    // Don't let the normal "on select action" handler get this event,
+    // as we handle it specially ourselves.
+    aEvent.stopPropagation();
+
+    var typeItem = this._list.selectedItem;
+    var handlerInfo = this._handledTypes[typeItem.type];
+
+    let onComplete = () => {
+      // Rebuild the actions menu so that we revert to the previous selection,
+      // or "Always ask" if the previous default application has been removed
+      this.rebuildActionsMenu();
+
+      // update the richlistitem too. Will be visible when selecting another row
+      typeItem.setAttribute("actionDescription",
+                            this._describePreferredAction(handlerInfo));
+      if (!this._setIconClassForPreferredAction(handlerInfo, typeItem)) {
+        typeItem.setAttribute("actionIcon",
+                              this._getIconURLForPreferredAction(handlerInfo));
+      }
+    };
+
+    gSubDialog.open("chrome://browser/content/preferences/applicationManager.xul",
+                    "resizable=no", handlerInfo, onComplete);
+
+  },
+
+  chooseApp: function(aEvent) {
+    // Don't let the normal "on select action" handler get this event,
+    // as we handle it specially ourselves.
+    aEvent.stopPropagation();
+
+    var handlerApp;
+    let chooseAppCallback = function(aHandlerApp) {
+      // Rebuild the actions menu whether the user picked an app or canceled.
+      // If they picked an app, we want to add the app to the menu and select it.
+      // If they canceled, we want to go back to their previous selection.
+      this.rebuildActionsMenu();
+
+      // If the user picked a new app from the menu, select it.
+      if (aHandlerApp) {
+        let typeItem = this._list.selectedItem;
+        let actionsMenu =
+          document.getAnonymousElementByAttribute(typeItem, "class", "actionsMenu");
+        let menuItems = actionsMenu.menupopup.childNodes;
+        for (let i = 0; i < menuItems.length; i++) {
+          let menuItem = menuItems[i];
+          if (menuItem.handlerApp && menuItem.handlerApp.equals(aHandlerApp)) {
+            actionsMenu.selectedIndex = i;
+            this.onSelectAction(menuItem);
+            break;
+          }
+        }
+      }
+    }.bind(this);
+
+    if (AppConstants.platform == "win") {
+      var params = {};
+      var handlerInfo = this._handledTypes[this._list.selectedItem.type];
+
+      if (isFeedType(handlerInfo.type)) {
+        // MIME info will be null, create a temp object.
+        params.mimeInfo = this._mimeSvc.getFromTypeAndExtension(handlerInfo.type,
+                                                   handlerInfo.primaryExtension);
+      } else {
+        params.mimeInfo = handlerInfo.wrappedHandlerInfo;
+      }
+
+      params.title         = this._prefsBundle.getString("fpTitleChooseApp");
+      params.description   = handlerInfo.description;
+      params.filename      = null;
+      params.handlerApp    = null;
+
+      let onAppSelected = () => {
+        if (this.isValidHandlerApp(params.handlerApp)) {
+          handlerApp = params.handlerApp;
+
+          // Add the app to the type's list of possible handlers.
+          handlerInfo.addPossibleApplicationHandler(handlerApp);
+        }
+
+        chooseAppCallback(handlerApp);
+      };
+
+      gSubDialog.open("chrome://global/content/appPicker.xul",
+                      null, params, onAppSelected);
+    } else {
+      let winTitle = this._prefsBundle.getString("fpTitleChooseApp");
+      let fp = Cc["@mozilla.org/filepicker;1"].createInstance(Ci.nsIFilePicker);
+      let fpCallback = function fpCallback_done(aResult) {
+        if (aResult == Ci.nsIFilePicker.returnOK && fp.file &&
+            this._isValidHandlerExecutable(fp.file)) {
+          handlerApp = Cc["@mozilla.org/uriloader/local-handler-app;1"].
+                       createInstance(Ci.nsILocalHandlerApp);
+          handlerApp.name = getFileDisplayName(fp.file);
+          handlerApp.executable = fp.file;
+
+          // Add the app to the type's list of possible handlers.
+          let handlerInfo = this._handledTypes[this._list.selectedItem.type];
+          handlerInfo.addPossibleApplicationHandler(handlerApp);
+
+          chooseAppCallback(handlerApp);
+        }
+      }.bind(this);
+
+      // Prompt the user to pick an app.  If they pick one, and it's a valid
+      // selection, then add it to the list of possible handlers.
+      fp.init(window, winTitle, Ci.nsIFilePicker.modeOpen);
+      fp.appendFilters(Ci.nsIFilePicker.filterApps);
+      fp.open(fpCallback);
+    }
+  },
+
+  // Mark which item in the list was last selected so we can reselect it
+  // when we rebuild the list or when the user returns to the prefpane.
+  onSelectionChanged: function() {
+    if (this._list.selectedItem)
+      this._list.setAttribute("lastSelectedType",
+                              this._list.selectedItem.getAttribute("type"));
+  },
+
+  _setIconClassForPreferredAction: function(aHandlerInfo, aElement) {
+    // If this returns true, the attribute that CSS sniffs for was set to something
+    // so you shouldn't manually set an icon URI.
+    // This removes the existing actionIcon attribute if any, even if returning false.
+    aElement.removeAttribute("actionIcon");
+
+    if (aHandlerInfo.alwaysAskBeforeHandling) {
+      aElement.setAttribute(APP_ICON_ATTR_NAME, "ask");
+      return true;
+    }
+
+    switch (aHandlerInfo.preferredAction) {
+      case Ci.nsIHandlerInfo.saveToDisk:
+        aElement.setAttribute(APP_ICON_ATTR_NAME, "save");
+        return true;
+
+      case Ci.nsIHandlerInfo.handleInternally:
+        if (isFeedType(aHandlerInfo.type)) {
+          aElement.setAttribute(APP_ICON_ATTR_NAME, "feed");
+          return true;
+        } else if (aHandlerInfo instanceof InternalHandlerInfoWrapper) {
+          aElement.setAttribute(APP_ICON_ATTR_NAME, "ask");
+          return true;
+        }
+        break;
+
+      case kActionUsePlugin:
+        aElement.setAttribute(APP_ICON_ATTR_NAME, "plugin");
+        return true;
+    }
+    aElement.removeAttribute(APP_ICON_ATTR_NAME);
+    return false;
+  },
+
+  _getIconURLForPreferredAction: function(aHandlerInfo) {
+    switch (aHandlerInfo.preferredAction) {
+      case Ci.nsIHandlerInfo.useSystemDefault:
+        return this._getIconURLForSystemDefault(aHandlerInfo);
+
+      case Ci.nsIHandlerInfo.useHelperApp:
+        let preferredApp = aHandlerInfo.preferredApplicationHandler;
+        if (this.isValidHandlerApp(preferredApp))
+          return this._getIconURLForHandlerApp(preferredApp);
+        // Explicit fall-through
+
+      // This should never happen, but if preferredAction is set to some weird
+      // value, then fall back to the generic application icon.
+      default:
+        return ICON_URL_APP;
+    }
+  },
+
+  _getIconURLForHandlerApp: function(aHandlerApp) {
+    if (aHandlerApp instanceof Ci.nsILocalHandlerApp)
+      return this._getIconURLForFile(aHandlerApp.executable);
+
+    if (aHandlerApp instanceof Ci.nsIWebHandlerApp)
+      return this._getIconURLForWebApp(aHandlerApp.uriTemplate);
+
+    if (aHandlerApp instanceof Ci.nsIWebContentHandlerInfo)
+      return this._getIconURLForWebApp(aHandlerApp.uri)
+
+    // We know nothing about other kinds of handler apps.
+    return "";
+  },
+
+  _getIconURLForFile: function(aFile) {
+    var fph = this._ioSvc.getProtocolHandler("file").
+              QueryInterface(Ci.nsIFileProtocolHandler);
+    var urlSpec = fph.getURLSpecFromFile(aFile);
+
+    return "moz-icon://" + urlSpec + "?size=16";
+  },
+
+  _getIconURLForWebApp: function(aWebAppURITemplate) {
+    var uri = this._ioSvc.newURI(aWebAppURITemplate, null, null);
+
+    // Unfortunately we can't use the favicon service to get the favicon,
+    // because the service looks in the annotations table for a record with
+    // the exact URL we give it, and users won't have such records for URLs
+    // they don't visit, and users won't visit the web app's URL template,
+    // they'll only visit URLs derived from that template (i.e. with %s
+    // in the template replaced by the URL of the content being handled).
+
+    if (/^https?$/.test(uri.scheme) && this._prefSvc.getBoolPref("browser.chrome.favicons"))
+      return uri.prePath + "/favicon.ico";
+
+    return "";
+  },
+
+  _getIconURLForSystemDefault: function(aHandlerInfo) {
+    // Handler info objects for MIME types on some OSes implement a property bag
+    // interface from which we can get an icon for the default app, so if we're
+    // dealing with a MIME type on one of those OSes, then try to get the icon.
+    if ("wrappedHandlerInfo" in aHandlerInfo) {
+      let wrappedHandlerInfo = aHandlerInfo.wrappedHandlerInfo;
+
+      if (wrappedHandlerInfo instanceof Ci.nsIMIMEInfo &&
+          wrappedHandlerInfo instanceof Ci.nsIPropertyBag) {
+        try {
+          let url = wrappedHandlerInfo.getProperty("defaultApplicationIconURL");
+          if (url)
+            return url + "?size=16";
+        }
+        catch (ex) {}
+      }
+    }
+
+    // If this isn't a MIME type object on an OS that supports retrieving
+    // the icon, or if we couldn't retrieve the icon for some other reason,
+    // then use a generic icon.
+    return ICON_URL_APP;
+  }
+
+};