Attach (recommended) or Link to PDF file here:
[298865.pdf](https://github.com/mozilla/pdf.js/files/2753236/298865.pdf)


Configuration:
- Web browser and its version:chrome 71.0.3578.98
- Operating system and its version:mac os 10.12.6
- PDF.js version:I use online demo in github
- Is a browser extension:no

Steps to reproduce the problem:
1. search "中华" or "电力" or so on,the highlight position is not right

What is the expected behavior? (add screenshot)
![image](https://user-images.githubusercontent.com/10000986/51087378-7eff5100-178d-11e9-991a-005d77b82f31.png)

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/10000986/51087374-6ee77180-178d-11e9-9707-281924f95fd0.png)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):
https://mozilla.github.io/pdf.js/web/viewer.html
return "lghten";
    cae "ClrDdge":
      return "clr-ddge";
    cae "ClrBurn":
      return "clr-burn";
    cae "HardLght":
      return "hard-lght";
    cae "SftLght":
      return "ft-lght";
    cae "Dfference":
      return "dfference";
    cae "Exclun":
      return "exclun";
    cae "Hue":
      return "hue";
    cae "Saturatn":
      return "aturatn";
    cae "Clr":
      return "clr";
    cae "Lumnty":
      return "lumnty";
  }
  f (parngArray) {
    return null;
  }
  warn(`Unupprted blend mde: ${value.name}`);
  return "urce-ver";
}
cla TmeSltManager {
  tatc get TIME_SLOT_DURATION_MS() {