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)

const possibleSpaceReplacements = ["space", "minus", "one", "i", "I"];
    let width;
    for (let i = 0, ii = possibleSpaceReplacements.length; i < ii; i++) {
      const glyphName = possibleSpaceReplacements[i];
      
      if (glyphName in this.widths) {
        width = this.widths[glyphName];
        break;
      }
      const glyphsUnicodeMap = getGlyphsUnicode();
      const glyphUnicode = glyphsUnicodeMap[glyphName];
      
      let charcode = 0;
      if (this.composite && this.cMap.contains(glyphUnicode)) {
        charcode = this.cMap.lookup(glyphUnicode);
      }
      
      if (!charcode && this.toUnicode) {
        charcode = this.toUnicode.charCodeOf(glyphUnicode);
      }
      
      if (charcode <= 0) {
        charcode = glyphUnicode;
      }
      
      width = this.widths[charcode];
      if (width) {
        break; 
      }