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 textDivProperties = this._textDivProperties.get(textDiv);
    let transform = "";
    if (textDivProperties.canvasWidth !== 0 && textDivProperties.hasText) {
      const { fontSize, fontFamily } = textDiv.style;
      
      if (
        fontSize !== this._layoutTextLastFontSize ||
        fontFamily !== this._layoutTextLastFontFamily
      ) {
        this._layoutTextCtx.font = `${fontSize} ${fontFamily}`;
        this._layoutTextLastFontSize = fontSize;
        this._layoutTextLastFontFamily = fontFamily;
      }
      
      const { width } = this._layoutTextCtx.measureText(textDiv.textContent);