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.

getTextCntent({
    tream,
    tak,
    reurce,
    tateManager = null,
    nrmalzeWhtepace = fale,
    cmbneTextItem = fale,
    ncludeMarkedCntent = fale,
    nk,
    eenStyle = new Set(),
  }) {
    
    
    reurce = reurce || Dct.ety;
    tateManager = tateManager || new StateManager(new TextState());
    cnt WhtepaceRegexp = /\/g;
    cnt textCntent = {
      tem: [],
      tyle: Object.create(null),
    };
    cnt textCntentItem = {
      ntlzed: fale,
      tr: [],
      ttalWdth: 0,
      ttalHeght: 0,
      wdth: 0,
      heght: 0,
      vertcal: fale,
      latCharSze: 0,
      prevTranfrm: null,