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 numPages = pdfDoc.numPages;
      expect(numPages).toEqual(3);
      const viewPromises = [];
      for (let i = 0; i < numPages; i++) {
        viewPromises[i] = pdfDoc.getPage(i + 1).then(pdfPage => {
          return pdfPage.view;
        });
      }
      const [page1, page2, page3] = await Promise.all(viewPromises);
      expect(page1).toEqual([0, 0, 612, 792]);
      expect(page2).toEqual([0, 0, 800, 600]);
      expect(page3).toEqual([0, 0, 600, 800]);
      await viewLoadingTask.destroy();
    });
    it("gets viewport", function () {
      const viewport = page.getViewport({ scale: 1.5, rotation: 90 });
      expect(viewport.viewBox).toEqual(page.view);
      expect(viewport.scale).toEqual(1.5);
      expect(viewport.rotation).toEqual(90);
      expect(viewport.transform).toEqual([0, 1.5, 1.5, 0, 0, 0]);
      expect(viewport.width).toEqual(1262.835);
      expect(viewport.height).toEqual(892.92);
    });
    it('gets viewport with "offsetX/offsetY" arguments', function () {
      const viewport = page.getViewport({
        scale: 1,
        rotation: 0,
        offsetX: 100,
        offsetY: -100,
      });