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)

for (let ii = data.length; i < ii; ) {
        const op = data[i++];
        
        
        if (op === 0x40) {
          
          n = data[i++];
          if (inFDEF || inELSE) {
            i += n;
          } else {
            for (j = 0; j < n; j++) {
              stack.push(data[i++]);
            }
          }
        } else if (op === 0x41) {
          
          n = data[i++];
          if (inFDEF || inELSE) {
            i += n * 2;
          } else {
            for (j = 0; j < n; j++) {
              b = data[i++];
              stack.push((b << 8) | data[i++]);
            }
          }
        } else if ((op & 0xf8) === 0xb0) {
          
          n = op - 0xb0 + 1;
          if (inFDEF || inELSE) {
            i += n;