code: function _captureFrame(editor) {
          // Capture the active position now if it was not captured earlier
          if ((activePosNotSynced || !jumpBackwardStack.length) && !jumpInProgress) {
              jumpBackwardStack.push(new NavigationFrame(editor, {ranges: editor._codeMirror.listSelections()}));
          }
      }
docs: Function to request a navigation frame creation explicitly.
  @private