function doSearchInOneFile(filepath, text, queryExpr, maxResultsToReturn) {
    var matches = getSearchMatches(text, queryExpr);
    setResults(filepath, {matches: matches}, maxResultsToReturn);
}
Finds search results in the given file and adds them to 'results'
@param {string} filepath
@param {string} text   contents of the file
@param {Object} queryExpr
@param {number} maxResultsToReturn the maximum of results that should be returned in the current search.