code: function() {
  			this._commitUndo();
  			var change, result = false;
  			this._ignoreUndo = true;
  			do {
  				if (this.index <= 0) {
  					break;
  				}
  				change = this.stack[--this.index];
  			} while (!(result = change.undo(this.view, true)));
  			this._ignoreUndo = false;
  			return result;
  		}
docs: Undo the last change in the stack.
  
  @return {Boolean} returns true if a change was un-done.
  
  @see orion.editor.UndoStack#redo
  @see orion.editor.UndoStack#canUndo