function _removeFileFromMRU(paneId, file) {
        var index,
            compare = function (record) {
                return (record.file === file && record.paneId === paneId);
            };

        // find and remove all instances
        do {
            index = _.findIndex(_mruList, compare);
            if (index !== -1) {
                _mruList.splice(index, 1);
            }
        } while (index !== -1);
    }
Removes a file from the global MRU list. Future versions of this
 implementation may support the ALL_PANES constant but FOCUS_PANE is not allowed
@param {!string} paneId - Must be a valid paneId (not a shortcut e.g. ALL_PANES)
     @ @param {File} file The file object to remove.
@private