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 

properties.fixedPitch = false;
    if (properties.builtInEncoding) {
      
      
      adjustToUnicode(properties, properties.builtInEncoding);
    }
    
    
    
    let glyphZeroId = 1;
    if (font instanceof CFFFont) {
      glyphZeroId = font.numGlyphs - 1;
    }
    const mapping = font.getGlyphMapping(properties);
    let newMapping = null;
    let newCharCodeToGlyphId = mapping;
    
    
    if (!properties.cssFontInfo) {
      newMapping = adjustMapping(
        mapping,
        font.hasGlyphId.bind(font),
        glyphZeroId
      );
      this.toFontChar = newMapping.toFontChar;
      newCharCodeToGlyphId = newMapping.charCodeToGlyphId;
    }
    const numGlyphs = font.numGlyphs;
    function getCharCodes(charCodeToGlyphId, glyphId) {