function createWorkingSetViewForPane($container, paneId) {
        var view = _views[paneId];
        if (!view) {
            view = new WorkingSetView($container, paneId);
            _views[view.paneId] = view;
        }
    }
Creates a new WorkingSetView object for the specified pane
@param {!jQuery} $container - the WorkingSetView's DOM parent node
@param {!string} paneId - the id of the pane the view is being created for