Attach (recommended) or Link to PDF file here:
[双引号不正常.pdf](https://github.com/mozilla/pdf.js/files/3533108/default.pdf)


Configuration:
- Web browser and its version:  IE11 , chrome 
- Operating system and its version:  win7
- PDF.js version:  master
- Is a browser extension: nothing 
teps to reproduce the problem:
1. viewer.html web  online preview


What is the expected behavior? (add screenshot)
Displayed in normal characters.

What went wrong? (add screenshot)
![20190823143813](https://user-images.githubusercontent.com/6269307/63571860-062e6600-c5b4-11e9-9fff-75d65cf6bade.png)

Not only the two characters I took screenshots, but also a lot of garbled Chinese punctuation. For example, the Chinese 《》 symbol. But these garbled characters only appear in some specific very old pdf files.

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):nothing 

funcId = stack.pop();
          ttContext.functionsDefined[funcId] = { data, i };
        } else if (op === 0x2d) {
          
          if (inFDEF) {
            inFDEF = false;
            lastEndf = i;
          } else {
            pc = callstack.pop();
            if (!pc) {
              warn("TT: ENDF bad stack");
              ttContext.hintsValid = false;
              return;
            }
            funcId = functionsCalled.pop();
            data = pc.data;
            i = pc.i;
            ttContext.functionsStackDeltas[funcId] = stack.length - pc.stackTop;
          }
        } else if (op === 0x89) {
          
          if (inFDEF || inELSE) {
            warn("TT: nested IDEFs not allowed");
            tooComplexToFollowFunctions = true;
          }
          inFDEF = true;
          
          lastDeff = i;
        } else if (op === 0x58) {