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 

if (
          (r.platform === 1 && r.encoding === 0 && r.language === 0) ||
          (r.platform === 3 && r.encoding === 1 && r.language === 0x409)
        ) {
          records.push(r);
        }
      }
      for (i = 0, ii = records.length; i < ii; i++) {
        const record = records[i];
        if (record.length <= 0) {
          continue; 
        }
        const pos = start + stringsStart + record.offset;
        if (pos + record.length > end) {
          continue; 
        }
        font.pos = pos;
        const nameIndex = record.name;
        if (record.encoding) {
          
          let str = "";
          for (let j = 0, jj = record.length; j < jj; j += 2) {
            str += String.fromCharCode(font.getUint16());
          }
          names[1][nameIndex] = str;
        } else {
          names[0][nameIndex] = font.getString(record.length);
        }
      }
      return names;