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)

constructor(error) {
    this.error = error;
    this.loadedName = "g_font_error";
    this.missingFile = true;
  }
  charsToGlyphs() {
    return [];
  }
  encodeString(chars) {
    return [chars];
  }
  exportData(extraProperties = false) {
    return { error: this.error };
  }
}
export { ErrorFont, Font };