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 

const accentGlyphName = StandardEncoding[seac[3]];
        const baseGlyphId = charset.indexOf(baseGlyphName);
        const accentGlyphId = charset.indexOf(accentGlyphName);
        if (baseGlyphId < 0 || accentGlyphId < 0) {
          continue;
        }
        const accentOffset = {
          x: seac[0] * matrix[0] + seac[1] * matrix[2] + matrix[4],
          y: seac[0] * matrix[1] + seac[1] * matrix[3] + matrix[5],
        };
        const charCodes = getCharCodes(mapping, glyphId);
        if (!charCodes) {
          
          
          continue;
        }
        for (let i = 0, ii = charCodes.length; i < ii; i++) {
          const charCode = charCodes[i];
          
          
          const charCodeToGlyphId = newMapping.charCodeToGlyphId;
          const baseFontCharCode = createCharCode(
            charCodeToGlyphId,
            baseGlyphId
          );
          const accentFontCharCode = createCharCode(
            charCodeToGlyphId,
            accentGlyphId
          );
          seacMap[charCode] = {