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)

override = override || {
    unitsPerEm: 0,
    yMax: 0,
    yMin: 0,
    ascent: 0,
    descent: 0,
  };
  let ulUnicodeRange1 = 0;
  let ulUnicodeRange2 = 0;
  let ulUnicodeRange3 = 0;
  let ulUnicodeRange4 = 0;
  let firstCharIndex = null;
  let lastCharIndex = 0;
  if (charstrings) {
    for (let code in charstrings) {
      code |= 0;
      if (firstCharIndex > code || !firstCharIndex) {
        firstCharIndex = code;