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 loadingTask = getDocument(buildGetDocumentParams("issue6106.pdf"));
      const pdfDoc = await loadingTask.promise;
      const javascript = await pdfDoc.getJavaScript();
      expect(javascript).toEqual([
        "this.print({bUI:true,bSilent:false,bShrinkToFit:true});",
      ]);
      expect(javascript[0]).toMatch(AutoPrintRegExp);
      await loadingTask.destroy();
    });
    it("gets hasJSActions, in document without javaScript", async function () {
      const hasJSActions = await pdfDocument.hasJSActions();
      expect(hasJSActions).toEqual(false);
    });
    it("gets hasJSActions, in document with javaScript", async function () {
      const loadingTask = getDocument(
        buildGetDocumentParams("doc_actions.pdf")
      );
      const pdfDoc = await loadingTask.promise;
      const hasJSActions = await pdfDoc.hasJSActions();
      expect(hasJSActions).toEqual(true);
      await loadingTask.destroy();
    });
    it("gets non-existent JSActions", async function () {
      const jsActions = await pdfDocument.getJSActions();
      expect(jsActions).toEqual(null);
    });
    it("gets JSActions", async function () {
      
      const loadingTask = getDocument(
        buildGetDocumentParams("doc_actions.pdf")