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):

let firstImgData = null;
      for (let i = 1; i <= pdfDoc.numPages; i++) {
        const pdfPage = await pdfDoc.getPage(i);
        const opList = await pdfPage.getOperatorList();
        const { commonObjs, objs } = pdfPage;
        const imgIndex = opList.fnArray.indexOf(OPS.paintImageXObject);
        const [objId, width, height] = opList.argsArray[imgIndex];
        if (i < NUM_PAGES_THRESHOLD) {
          expect(objId).toEqual(`img_p${i - 1}_1`);
          expect(objs.has(objId)).toEqual(true);
          expect(commonObjs.has(objId)).toEqual(false);
        } else {
          expect(objId).toEqual(
            `g_${loadingTask.docId}_img_p${NUM_PAGES_THRESHOLD - 1}_1`
          );
          expect(objs.has(objId)).toEqual(false);
          expect(commonObjs.has(objId)).toEqual(true);
        }
        expect(width).toEqual(EXPECTED_WIDTH);
        expect(height).toEqual(EXPECTED_HEIGHT);
        
        if (i === 1) {
          firstImgData = objs.get(objId);
          expect(firstImgData.width).toEqual(EXPECTED_WIDTH);
          expect(firstImgData.height).toEqual(EXPECTED_HEIGHT);
          expect(firstImgData.kind).toEqual(ImageKind.RGB_24BPP);
          expect(firstImgData.data instanceof Uint8ClampedArray).toEqual(true);
          expect(firstImgData.data.length).toEqual(25245000);
        } else {
          const objsPool = i >= NUM_PAGES_THRESHOLD ? commonObjs : objs;