code: function InstalledViewModel() {
          ExtensionManagerViewModel.call(this);
  
          // when registry is downloaded, sort extensions again - those with updates will be before others
          var self = this;
          ExtensionManager.on("registryDownload." + this.source, function () {
              self._sortFullSet();
              self._setInitialFilter();
          });
      }
docs: The model for the ExtensionManagerView that is responsible for handling previously-installed extensions.
  This extends ExtensionManagerViewModel.
  Must be disposed with dispose() when done.
  
  Events:
  - change - triggered when the data for a given extension changes. Second parameter is the extension id.
  - filter - triggered whenever the filtered set changes (including on initialize).
  
  @constructor