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)

"hmtx",
      (function fontFieldsHmtx() {
        const charstrings = font.charstrings;
        const cffWidths = font.cff ? font.cff.widths : null;
        let hmtx = "\x00\x00\x00\x00"; 
        for (let i = 1, ii = numGlyphs; i < ii; i++) {
          let width = 0;
          if (charstrings) {
            const charstring = charstrings[i - 1];
            width = "width" in charstring ? charstring.width : 0;
          } else if (cffWidths) {
            width = Math.ceil(cffWidths[i] || 0);
          }
          hmtx += string16(width) + string16(0);
        }
        return hmtx;
      })()
    );
    
    builder.addTable(
      "maxp",
      "\x00\x00\x50\x00" + string16(numGlyphs) 
    ); 
    
    builder.addTable("name", createNameTable(fontName));
    
    builder.addTable("post", createPostTable(properties));
    return builder.toArray();
  }
  get spaceWidth() {