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
expect(info.PDFFormatVersion).toEqual("1.7");
      expect(info.IsLinearized).toEqual(false);
      expect(info.IsAcroFormPresent).toEqual(false);
      expect(info.IsXFAPresent).toEqual(false);
      expect(info.IsCollectionPresent).toEqual(false);
      expect(info.IsSignaturesPresent).toEqual(false);
      expect(metadata instanceof Metadata).toEqual(true);
      expect(metadata.get("dc:title")).toEqual("Basic API Test");
      expect(contentDispositionFilename).toEqual(null);
      expect(contentLength).toEqual(basicApiFileLength);
    });
    it("gets metadata, with custom info dict entries", async function () {
      const loadingTask = getDocument(
        buildGetDocumentParams("tracemonkey.pdf")
      );
      const pdfDoc = await loadingTask.promise;
      const { info, metadata, contentDispositionFilename, contentLength } =
        await pdfDoc.getMetadata();
      expect(info.Creator).toEqual("TeX");
      expect(info.Producer).toEqual("pdfeTeX-1.21a");
      expect(info.CreationDate).toEqual("D:20090401163925-07'00'");
      
      const custom = info.Custom;
      expect(typeof custom === "object" && custom !== null).toEqual(true);
      expect(custom["PTEX.Fullbanner"]).toEqual(
        "This is pdfeTeX, " +
          "Version 3.141592-1.21a-2.2 (Web2C 7.5.4) kpathsea version 3.5.6"
      );