Attach (recommended) or Link to PDF file here:
[example.pdf](https://github.com/mozilla/pdf.js/files/6916129/example.pdf)

Configuration:
- Web browser and its version: Chrome, Firefox
- Operating system and its version: all
- PDF.js version: various versions, including 2.11.54
- Is a browser extension: no

Screenshot with visible textLayer:
![Screenshot from 2021-08-02 13-05-03](https://user-images.githubusercontent.com/6362989/127844878-f85e291f-2060-4028-be09-7835f32ccfaa.png)

Which means some letters at the beginning/end of text selection are missing when copying text.

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