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
expectedStreamTypes[StreamType.FLATE] = true;
      const expectedFontTypes = {};
      expectedFontTypes[FontType.TYPE1STANDARD] = true;
      expectedFontTypes[FontType.CIDFONTTYPE2] = true;
      expect(stats).toEqual({
        streamTypes: expectedStreamTypes,
        fontTypes: expectedFontTypes,
      });
    });
    it("gets page stats after parsing page, without `pdfBug` set", async function () {
      await page.getOperatorList();
      expect(page.stats).toEqual(null);
    });
    it("gets page stats after parsing page, with `pdfBug` set", async function () {
      const loadingTask = getDocument(
        buildGetDocumentParams(basicApiFileName, { pdfBug: true })
      );
      const pdfDoc = await loadingTask.promise;
      const pdfPage = await pdfDoc.getPage(1);
      await pdfPage.getOperatorList();
      const stats = pdfPage.stats;
      expect(stats instanceof StatTimer).toEqual(true);
      expect(stats.times.length).toEqual(1);
      const [statEntry] = stats.times;
      expect(statEntry.name).toEqual("Page Request");
      expect(statEntry.end - statEntry.start).toBeGreaterThanOrEqual(0);
      await loadingTask.destroy();
    });
    it("gets page stats after rendering page, with `pdfBug` set", async function () {
      const loadingTask = getDocument(