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 

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;