code: function ExtensionManagerViewModel() {
          this._handleStatusChange = this._handleStatusChange.bind(this);
  
          // Listen for extension status changes.
          ExtensionManager
              .on("statusChange." + this.source, this._handleStatusChange)
              .on("registryUpdate." + this.source, this._handleStatusChange);
      }
docs: The base model for the ExtensionManagerView. Keeps track of the extensions that are currently visible
  and manages sorting/filtering them. 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