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
constructor({
    textContent,
    textContentStream,
    container,
    viewport,
    textDivs,
    textContentItemsStr,
    enhanceTextSelection,
  }) {
    this._textContent = textContent;
    this._textContentStream = textContentStream;
    this._container = container;
    this._document = container.ownerDocument;
    this._viewport = viewport;
    this._textDivs = textDivs || [];
    this._textContentItemsStr = textContentItemsStr || [];
    this._enhanceTextSelection = !!enhanceTextSelection;
    this._fontInspectorEnabled = !!globalThis.FontInspector?.enabled;
    this._reader = null;
    this._layoutTextLastFontSize = null;
    this._layoutTextLastFontFamily = null;
    this._layoutTextCtx = null;