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
b.y1 = width - e.right;
    b.x2 = box.bottom;
    b.y2 = width - e.left;
    b.index = i;
    b.x1New = undefined;
    b.x2New = undefined;
  });
  expandBoundsLTR(height, bounds);
  for (const b of bounds) {
    const i = b.index;
    expanded[i].top = b.x1New;
    expanded[i].bottom = b.x2New;
  }
  return expanded;
}
function expandBoundsLTR(width, bounds) {
  
  bounds.sort(function (a, b) {
    return a.x1 - b.x1 || a.index - b.index;
  });
  
  const fakeBoundary = {
    x1: -Infinity,
    y1: -Infinity,
    x2: 0,
    y2: Infinity,
    index: -1,
    x1New: 0,
    x2New: 0,
  };