Viewer:  https://mozilla.github.io/pdf.js/web/viewer.html
Chrome on Windows 10
When the attached PDF file is viewed, some of the fonts display as garbled text. 
[Arial, Courier, Times New Roman]
The file views correctly in Adobe Reader.
[fff.pdf](https://github.com/mozilla/pdf.js/files/4652174/fff.pdf)

tables.maxp.data[5] = numGlyphsOut & 255;
    const hintsValid = sanitizeTTPrograms(
      tables.fpgm,
      tables.prep,
      tables["cvt "],
      maxFunctionDefs
    );
    if (!hintsValid) {
      delete tables.fpgm;
      delete tables.prep;
      delete tables["cvt "];
    }
    
    
    sanitizeMetrics(
      font,
      tables.hhea,
      tables.hmtx,
      tables.head,
      numGlyphsOut,
      dupFirstEntry
    );
    if (!tables.head) {
      throw new FormatError('Required "head" table is not found');
    }
    sanitizeHead(tables.head, numGlyphs, isTrueType ? tables.loca.length : 0);
    let missingGlyphs = Object.create(null);
    if (isTrueType) {
      const isGlyphLocationsLong = int16(
        tables.head.data[50],