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
return pdfDoc.getOpenAction();
        })
        .then(function (openAction) {
          expect(openAction.dest).toBeUndefined();
          expect(openAction.action).toEqual("Print");
          return loadingTask2.destroy();
        });
      await Promise.all([promise1, promise2]);
    });
    it("gets non-existent attachments", async function () {
      const attachments = await pdfDocument.getAttachments();
      expect(attachments).toEqual(null);
    });
    it("gets attachments", async function () {
      const loadingTask = getDocument(buildGetDocumentParams("attachment.pdf"));
      const pdfDoc = await loadingTask.promise;
      const attachments = await pdfDoc.getAttachments();
      const attachment = attachments["foo.txt"];
      expect(attachment.filename).toEqual("foo.txt");
      expect(attachment.content).toEqual(
        new Uint8Array([98, 97, 114, 32, 98, 97, 122, 32, 10])
      );
      await loadingTask.destroy();
    });
    it("gets javascript", async function () {
      const javascript = await pdfDocument.getJavaScript();
      expect(javascript).toEqual(null);
    });
    it("gets javascript with printing instructions (JS action)", async function () {