Attach (recommended) or Link to PDF file here:
[shading_pattern.pdf](https://github.com/mozilla/pdf.js/files/1532598/shading_pattern.pdf)

Configuration:
- Web browser and its version: Firefox 57.0
- Operating system and its version: Debian GNU/Linux 9 64-bit
- PDF.js version: tried with Firefox's 1.9.583 and with online viewer 2.0.185
- Is a browser extension: no

Steps to reproduce the problem:
1. Open the attached file with the online viewer https://mozilla.github.io/pdf.js/web/viewer.html

What is the expected behavior? (add screenshot)
![image](https://user-images.githubusercontent.com/11061462/33626267-d9a57dee-d9d8-11e7-8712-cfa17c038259.png)
(Image captured from Adobe Reader CS.) The shading needs to be inside the letters.

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/11061462/33626285-eaabd462-d9d8-11e7-94e2-96480b57750d.png)
The shading seems to be displaced and upside-down, for it does not cover all the characters of the word.

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

this.ctx.closePath();
  }
  stroke(consumePath) {
    consumePath = typeof consumePath !== "undefined" ? consumePath : true;
    const ctx = this.ctx;
    const strokeColor = this.current.strokeColor;
    
    
    ctx.globalAlpha = this.current.strokeAlpha;
    if (this.contentVisible) {
      if (typeof strokeColor === "object" && strokeColor?.getPattern) {
        const lineWidth = this.getSinglePixelWidth();
        ctx.save();
        ctx.strokeStyle = strokeColor.getPattern(
          ctx,
          this,
          ctx.mozCurrentTransformInverse
        );
        
        ctx.lineWidth = Math.max(lineWidth, this.current.lineWidth);
        ctx.stroke();
        ctx.restore();
      } else {
        const lineWidth = this.getSinglePixelWidth();
        if (lineWidth < 0 && -lineWidth >= this.current.lineWidth) {
          
          
          ctx.save();
          ctx.resetTransform();
          ctx.lineWidth = Math.round(this._combinedScaleFactor);