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):

changedHorizon[0].start = boundary.y1;
      changedHorizon.unshift({
        start: horizon[i].start,
        end: boundary.y1,
        boundary: horizon[i].boundary,
      });
    }
    if (boundary.y2 < horizon[j].end) {
      changedHorizon[changedHorizon.length - 1].end = boundary.y2;
      changedHorizon.push({
        start: boundary.y2,
        end: horizon[j].end,
        boundary: horizon[j].boundary,
      });
    }
    
    
    
    for (q = i; q <= j; q++) {
      horizonPart = horizon[q];
      affectedBoundary = horizonPart.boundary;
      if (affectedBoundary.x2New !== undefined) {
        continue;
      }
      let used = false;
      for (
        k = i - 1;
        !used && k >= 0 && horizon[k].start >= affectedBoundary.y1;
        k--
      ) {