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
this._pdfDocument = pdfDocument;
  }
  get pagesCount() {
    return this._pdfDocument.numPages;
  }
  get page() {
    return this._page;
  }
  set page(value) {
    this._page = value;
  }
}
async function initPdfFindController(filename) {
  const loadingTask = getDocument(
    buildGetDocumentParams(filename || tracemonkeyFileName)
  );
  const pdfDocument = await loadingTask.promise;
  const eventBus = new EventBus();
  const linkService = new MockLinkService();
  linkService.setDocument(pdfDocument);
  const pdfFindController = new PDFFindController({
    linkService,
    eventBus,
  });
  pdfFindController.setDocument(pdfDocument); 
  return { eventBus, pdfFindController };
}
function testSearch({
  eventBus,
  pdfFindController,