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)

}
    width = width || this.defaultWidth;
    return shadow(this, "spaceWidth", width);
  }
  /**
   * @private
   */
  _charToGlyph(charcode, isSpace = false) {
    let fontCharCode, width, operatorListId;
    let widthCode = charcode;
    if (this.cMap && this.cMap.contains(charcode)) {
      widthCode = this.cMap.lookup(charcode);
    }
    width = this.widths[widthCode];
    width = isNum(width) ? width : this.defaultWidth;
    const vmetric = this.vmetrics && this.vmetrics[widthCode];
    let unicode = this.toUnicode.get(charcode) || charcode;
    if (typeof unicode === "number") {
      unicode = String.fromCharCode(unicode);
    }
    let isInFont = this.toFontChar[charcode] !== undefined;
    
    
    fontCharCode = this.toFontChar[charcode] || charcode;
    if (this.missingFile) {
      const glyphName =
        this.differences[charcode] || this.defaultEncoding[charcode];
      if (
        (glyphName === ".notdef" || glyphName === "") &&
        this.type === "Type1"