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
const bounds = boxes.map(function (box, i) {
    return {
      x1: box.left,
      y1: box.top,
      x2: box.right,
      y2: box.bottom,
      index: i,
      x1New: undefined,
      x2New: undefined,
    };
  });
  expandBoundsLTR(width, bounds);
  const expanded = new Array(boxes.length);
  for (const b of bounds) {
    const i = b.index;
    expanded[i] = {
      left: b.x1New,
      top: 0,
      right: b.x2New,
      bottom: 0,
    };
  }
  
  
  boxes.map(function (box, i) {
    const e = expanded[i],
      b = bounds[i];
    b.x1 = box.top;