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
buildGetDocumentParams("issue9972-3.pdf")
      );
      const promise2 = loadingTask2.promise.then(function (pdfDoc) {
        return pdfDoc.getPermissions();
      });
      const totalPermissionCount = Object.keys(PermissionFlag).length;
      const permissions = await Promise.all([promise0, promise1, promise2]);
      expect(permissions[0].length).toEqual(totalPermissionCount - 1);
      expect(
        permissions[0].includes(PermissionFlag.MODIFY_CONTENTS)
      ).toBeFalsy();
      expect(permissions[1].length).toEqual(totalPermissionCount - 2);
      expect(permissions[1].includes(PermissionFlag.PRINT)).toBeFalsy();
      expect(
        permissions[1].includes(PermissionFlag.PRINT_HIGH_QUALITY)
      ).toBeFalsy();
      expect(permissions[2].length).toEqual(totalPermissionCount - 1);
      expect(permissions[2].includes(PermissionFlag.COPY)).toBeFalsy();
      await Promise.all([
        loadingTask0.destroy(),
        loadingTask1.destroy(),
        loadingTask2.destroy(),
      ]);
    });
    it("gets metadata", async function () {
      const { info, metadata, contentDispositionFilename, contentLength } =
        await pdfDocument.getMetadata();
      expect(info.Title).toEqual("Basic API Test");
      
      expect(info.Custom).toEqual(undefined);