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 

"defaultWidth",
  "descent",
  "fallbackName",
  "fontMatrix",
  "fontType",
  "isMonospace",
  "isSerifFont",
  "isType3Font",
  "italic",
  "loadedName",
  "mimetype",
  "missingFile",
  "name",
  "remeasure",
  "subtype",
  "type",
  "vertical",
];
const EXPORT_DATA_EXTRA_PROPERTIES = [
  "cMap",
  "defaultEncoding",
  "differences",
  "isSymbolicFont",
  "seacMap",
  "toFontChar",
  "toUnicode",
  "vmetrics",
  "widths",
];
function adjustWidths(properties) {