function _makePaneMostRecent(paneId) {
        var pane = _getPane(paneId);

        if (pane.getCurrentlyViewedFile()) {
            _makeFileMostRecent(paneId, pane.getCurrentlyViewedFile());
        }
    }
Makes the Pane's current file the most recent
@param {!string} paneId - id of the pane to make the file most recent, or ACTIVE_PANE
@param {!File} file - File object to make most recent
@private