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):

});
      await loadingTask.destroy();
    });
    it("gets empty structure tree", async function () {
      const tree = await page.getStructTree();
      expect(tree).toEqual(null);
    });
    it("gets simple structure tree", async function () {
      const loadingTask = getDocument(
        buildGetDocumentParams("structure_simple.pdf")
      );
      const pdfDoc = await loadingTask.promise;
      const pdfPage = await pdfDoc.getPage(1);
      const tree = await pdfPage.getStructTree();
      expect(tree).toEqual({
        role: "Root",
        children: [
          {
            role: "Document",
            children: [
              {
                role: "H1",
                children: [
                  {
                    role: "NonStruct",
                    children: [{ type: "content", id: "page2R_mcid0" }],
                  },
                ],
              },
              {