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):

}
  setFlatness(flatness) {
    
  }
  setGState(states) {
    for (let i = 0, ii = states.length; i < ii; i++) {
      const state = states[i];
      const key = state[0];
      const value = state[1];
      switch (key) {
        case "LW":
          this.setLineWidth(value);
          break;
        case "LC":
          this.setLineCap(value);
          break;
        case "LJ":
          this.setLineJoin(value);
          break;
        case "ML":
          this.setMiterLimit(value);
          break;
        case "D":
          this.setDash(value[0], value[1]);
          break;