Attach (recommended) or Link to PDF file here:
[Hong Kong Aircraft Engineering Company Limited_1511417616.1 2.pdf](https://github.com/mozilla/pdf.js/files/1539395/Hong.Kong.Aircraft.Engineering.Company.Limited_1511417616.1.2.pdf)


Configuration:
- Web browser and its version: Chrome: 63 
- Operating system and its version: windows and macOs
- PDF.js version: 2.0.185
- Is a browser extension: No

Steps to reproduce the problem:
1. Upload the above PDF and search for "article 1"
2. PDF.js showing only **2** match But actually **4** times available.   

What is the expected behavior? (add screenshot)

![screen shot 2017-12-07 at 7](https://user-images.githubusercontent.com/6101789/33720106-ed404576-db88-11e7-9c19-cf6aea74e9f3.png)



What went wrong? (add screenshot)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

expect(outline).toEqual(null);
      await loadingTask.destroy();
    });
    it("gets outline", async function () {
      const outline = await pdfDocument.getOutline();
      
      expect(Array.isArray(outline)).toEqual(true);
      expect(outline.length).toEqual(2);
      
      const outlineItem = outline[1];
      expect(outlineItem.title).toEqual("Chapter 1");
      expect(Array.isArray(outlineItem.dest)).toEqual(true);
      expect(outlineItem.url).toEqual(null);
      expect(outlineItem.unsafeUrl).toBeUndefined();
      expect(outlineItem.newWindow).toBeUndefined();
      expect(outlineItem.bold).toEqual(true);
      expect(outlineItem.italic).toEqual(false);
      expect(outlineItem.color).toEqual(new Uint8ClampedArray([0, 64, 128]));
      expect(outlineItem.items.length).toEqual(1);
      expect(outlineItem.items[0].title).toEqual("Paragraph 1.1");
    });
    it("gets outline containing a URL", async function () {
      const loadingTask = getDocument(buildGetDocumentParams("issue3214.pdf"));
      const pdfDoc = await loadingTask.promise;
      const outline = await pdfDoc.getOutline();
      expect(Array.isArray(outline)).toEqual(true);
      expect(outline.length).toEqual(5);
      const outlineItemTwo = outline[2];
      expect(typeof outlineItemTwo.title).toEqual("string");
      expect(outlineItemTwo.dest).toEqual(null);