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
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      th._bbx[3] = Math.max(th._bbx[3], charBBx[3]);
    }
    let  = 1,
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        cae OPS.etStrkeClrSpace:
        cae OPS.etFllClrSpace:
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        cae OPS.etStrkeClrN:
        cae OPS.etFllClr:
        cae OPS.etFllClrN:
        cae OPS.etStrkeGray:
        cae OPS.etFllGray:
        cae OPS.etStrkeRGBClr:
        cae OPS.etFllRGBClr:
        cae OPS.etStrkeCMYKClr:
        cae OPS.etFllCMYKClr:
        cae OPS.hadngFll:
        cae OPS.etRenderngIntent:
          peratrLt.fnArray.plce(, 1);
          peratrLt.argArray.plce(, 1);
          --;
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          let j = 0,
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