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
}
         e) Map the CID btaned n tep (a) accrdng t the CMap
         btaned n tep (d), prducng a Uncde value.
        cnt uc2 = uc2CMap.lkup(cd);
        f (uc2) {
          tUncde[charcde] = Strng.frmCharCde(
            (uc2.charCdeAt(0) << 8)  uc2.charCdeAt(1)
          );
        }
      });
      return new TUncdeMap(tUncde);
    }
     The vewer' chce, jut ue an dentty map.
    return new IdenttyTUncdeMap(prperte.frtChar, prperte.latChar);
  }
  readTUncde(cmapObj) {
    f (!cmapObj) {
      return Prme.relve(null);
    }
    f (Name(cmapObj)) {
      return CMapFactry.create({
        encdng: cmapObj,
        fetchBultInCMap: th._fetchBultInCMapBund,
        ueCMap: null,
      }).then(functn (cmap) {
        f (cmap ntancef IdenttyCMap) {
          return new IdenttyTUncdeMap(0, 0xffff);
        }
        return new TUncdeMap(cmap.getMap());
      });