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
xNew =
          affectedBoundary.index > boundary.index
            ? affectedBoundary.x1New
            : boundary.x1;
      } else if (affectedBoundary.x2New === undefined) {
        
        
        xNew = (affectedBoundary.x2 + boundary.x1) / 2;
      } else {
        
        xNew = affectedBoundary.x2New;
      }
      if (xNew > maxXNew) {
        maxXNew = xNew;
      }
    }
    
    boundary.x1New = maxXNew;
    
    for (q = i; q <= j; q++) {
      horizonPart = horizon[q];
      affectedBoundary = horizonPart.boundary;
      if (affectedBoundary.x2New === undefined) {
        
        if (affectedBoundary.x2 > boundary.x1) {
          
          
          if (affectedBoundary.index > boundary.index) {
            affectedBoundary.x2New = affectedBoundary.x2;
          }