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):

c.scale(1 / width, -1 / height);
    c.translate(0, -height);
    c.beginPath();
    for (let k = 0, kk = outlines.length; k < kk; k++) {
      const o = outlines[k];
      c.moveTo(o[0], o[1]);
      for (let l = 2, ll = o.length; l < ll; l += 2) {
        c.lineTo(o[l], o[l + 1]);
      }
    }
    c.fill();
    c.beginPath();
    c.restore();
  };
  return drawOutline;
}
class CanvasExtraState {
  constructor(width, height) {
    
    this.alphaIsShape = false;
    this.fontSize = 0;
    this.fontSizeScale = 1;
    this.textMatrix = IDENTITY_MATRIX;
    this.textMatrixScale = 1;
    this.fontMatrix = FONT_IDENTITY_MATRIX;
    this.leading = 0;
    
    this.x = 0;
    this.y = 0;