code: function _notifyActiveEditorChanged(current) {
          // Skip if the Editor that gained focus was already the most recently focused editor.
          // This may happen e.g. if the window loses then regains focus.
          if (_lastFocusedEditor === current) {
              return;
          }
          var previous = _lastFocusedEditor;
          _lastFocusedEditor = current;
  
          exports.trigger("activeEditorChange", current, previous);
      }
docs: Editor focus handler to change the currently active editor
  @private
  @param {?Editor} current - the editor that will be the active editor