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
const page1 = loadingTask.promise.then(function (pdfDoc) {
        return pdfDoc.getPage(1).then(
          function (pdfPage) {
            expect(pdfPage instanceof PDFPageProxy).toEqual(true);
            expect(pdfPage.ref).toEqual({ num: 6, gen: 0 });
          },
          function (reason) {
            throw new Error("shall not fail for valid page");
          }
        );
      });
      const page2 = loadingTask.promise.then(function (pdfDoc) {
        return pdfDoc.getPage(2).then(
          function (pdfPage) {
            throw new Error("shall fail for invalid page");
          },
          function (reason) {
            expect(reason instanceof Error).toEqual(true);
            expect(reason.message).toEqual(
              "Pages tree contains circular reference."
            );
          }
        );
      });
      await Promise.all([page1, page2]);
      await loadingTask.destroy();
    });
    it("gets page index", async function () {
      const ref = { num: 17, gen: 0 }; 
      const pageIndex = await pdfDocument.getPageIndex(ref);