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)

ttContext.hintsValid = false;
                  return;
                }
                stack.length = newStackLength;
              } else if (
                funcId in ttContext.functionsDefined &&
                !functionsCalled.includes(funcId)
              ) {
                callstack.push({ data, i, stackTop: stack.length - 1 });
                functionsCalled.push(funcId);
                pc = ttContext.functionsDefined[funcId];
                if (!pc) {
                  warn("TT: CALL non-existent function");
                  ttContext.hintsValid = false;
                  return;
                }
                data = pc.data;
                i = pc.i;
              }
            }
          }
        } else if (op === 0x2c && !tooComplexToFollowFunctions) {
          
          if (inFDEF || inELSE) {
            warn("TT: nested FDEFs not allowed");
            tooComplexToFollowFunctions = true;
          }
          inFDEF = true;
          
          lastDeff = i;