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 ttContext = {
        functionsDefined: [],
        functionsUsed: [],
        functionsStackDeltas: [],
        tooComplexToFollowFunctions: false,
        hintsValid: true,
      };
      if (fpgm) {
        sanitizeTTProgram(fpgm, ttContext);
      }
      if (prep) {
        sanitizeTTProgram(prep, ttContext);
      }
      if (fpgm) {
        checkInvalidFunctions(ttContext, maxFunctionDefs);
      }
      if (cvt && cvt.length & 1) {
        const cvtData = new Uint8Array(cvt.length + 1);
        cvtData.set(cvt.data);
        cvt.data = cvtData;
      }
      return ttContext.hintsValid;
    }