function findInWorkingSet(paneId, fullPath) {
        return _doFindInWorkingSet(paneId, fullPath, "findInViewList");
    }
Gets the index of the file matching fullPath in the workingset
@param {!string} paneId - id of the pane in which to search or ALL_PANES or ACTIVE_PANE
@param {!string} fullPath - full path of the file to search for
@return {number} index, -1 if not found.