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)

}
          if (unicodeOrCharCode === undefined) {
            
            
            if (
              !properties.glyphNames &&
              properties.hasIncludedToUnicodeMap &&
              !(this.toUnicode instanceof IdentityToUnicodeMap)
            ) {
              const unicode = this.toUnicode.get(charCode);
              if (unicode) {
                unicodeOrCharCode = unicode.codePointAt(0);
              }
            }
            if (unicodeOrCharCode === undefined) {
              continue; 
            }
          }
          for (let i = 0; i < cmapMappingsLength; ++i) {
            if (cmapMappings[i].charCode !== unicodeOrCharCode) {
              continue;
            }
            charCodeToGlyphId[charCode] = cmapMappings[i].glyphId;
            break;
          }
        }
      } else if (cmapPlatformId === 0) {
        
        for (let i = 0; i < cmapMappingsLength; ++i) {
          charCodeToGlyphId[cmapMappings[i].charCode] = cmapMappings[i].glyphId;