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
buildGetDocumentParams("issue8702.pdf", {
            stopAtErrors: true,
          })
        );
        const result1 = loadingTask1.promise.then(pdfDoc => {
          return pdfDoc.getPage(1).then(pdfPage => {
            return pdfPage.getOperatorList().then(opList => {
              expect(opList.fnArray.length).toBeGreaterThan(100);
              expect(opList.argsArray.length).toBeGreaterThan(100);
              expect(opList.lastChunk).toEqual(true);
              return loadingTask1.destroy();
            });
          });
        });
        const result2 = loadingTask2.promise.then(pdfDoc => {
          return pdfDoc.getPage(1).then(pdfPage => {
            return pdfPage.getOperatorList().then(opList => {
              expect(opList.fnArray.length).toEqual(0);
              expect(opList.argsArray.length).toEqual(0);
              expect(opList.lastChunk).toEqual(true);
              return loadingTask2.destroy();
            });
          });
        });
        await Promise.all([result1, result2]);
      }
    );
    it("gets operator list, containing Annotation-operatorLists", async function () {
      const loadingTask = getDocument(
        buildGetDocumentParams("annotation-line.pdf")