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(
        worker1.port !== worker2.port &&
          worker1.port !== worker3.port &&
          worker2.port !== worker3.port
      ).toEqual(true);
      worker1.destroy();
      worker2.destroy();
      worker3.destroy();
    });
    it("gets current workerSrc", function () {
      if (isNodeJS) {
        pending("Worker is not supported in Node.js.");
      }
      const workerSrc = PDFWorker.workerSrc;
      expect(typeof workerSrc).toEqual("string");
      expect(workerSrc).toEqual(GlobalWorkerOptions.workerSrc);
    });
  });
  describe("PDFDocument", function () {
    let pdfLoadingTask, pdfDocument;
    beforeAll(async function () {
      pdfLoadingTask = getDocument(basicApiGetDocumentParams);
      pdfDocument = await pdfLoadingTask.promise;
    });
    afterAll(async function () {
      await pdfLoadingTask.destroy();
    });
    it("gets number of pages", function () {
      expect(pdfDocument.numPages).toEqual(3);
    });