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
return this._capability.promise;
  }
  /**
   * Cancel rendering of the textLayer.
   */
  cancel() {
    this._canceled = true;
    if (this._reader) {
      this._reader
        .cancel(new AbortException("TextLayer task cancelled."))
        .catch(() => {
          
        });
      this._reader = null;
    }
    if (this._renderTimer !== null) {
      clearTimeout(this._renderTimer);
      this._renderTimer = null;
    }
    this._capability.reject(new Error("TextLayer task cancelled."));
  }
  /**
   * @private
   */
  _processItems(items, styleCache) {