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 (op >= 0x71 && op <= 0x75) {
            n = stack.pop();
            if (!isNaN(n)) {
              stackDelta = -n * 2;
            }
          }
          while (stackDelta < 0 && stack.length > 0) {
            stack.pop();
            stackDelta++;
          }
          while (stackDelta > 0) {
            stack.push(NaN); 
            stackDelta--;
          }
        }
      }
      ttContext.tooComplexToFollowFunctions = tooComplexToFollowFunctions;
      const content = [data];
      if (i > data.length) {
        content.push(new Uint8Array(i - data.length));
      }
      if (lastDeff > lastEndf) {
        warn("TT: complementing a missing function tail");
        
        
        content.push(new Uint8Array([0x22, 0x2d]));
      }
      foldTTTable(table, content);
    }
    function checkInvalidFunctions(ttContext, maxFunctionDefs) {