code: function getActiveFilter() {
          var filterSets        = PreferencesManager.get("fileFilters") || [],
              activeFilterIndex = PreferencesManager.getViewState("activeFileFilter"),
              oldFilter         = PreferencesManager.getViewState("search.exclusions") || [],
              activeFilter      = null;
  
          if (activeFilterIndex === undefined && oldFilter.length) {
              activeFilter = { name: "", patterns: oldFilter };
              activeFilterIndex = _getFilterIndex(filterSets, activeFilter);
  
              // Migrate the old filter into the new filter storage
              if (activeFilterIndex === -1) {
                  activeFilterIndex = filterSets.length;
                  filterSets.push(activeFilter);
                  PreferencesManager.set("fileFilters", filterSets);
              }
              PreferencesManager.setViewState("activeFileFilter", activeFilterIndex);
          } else if (activeFilterIndex > -1 && activeFilterIndex < filterSets.length) {
              activeFilter = filterSets[activeFilterIndex];
          }
  
          return activeFilter;
      }
docs: A search filter is an array of one or more glob strings. The filter must be 'compiled' via compile()
  before passing to filterPath()/filterFileList().
  @return {?{name: string, patterns: Array.<string>}}