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):

[x, y] = Util.applyTransform([x, y], transform);
    this.minX = Math.min(this.minX, x);
    this.minY = Math.min(this.minY, y);
    this.maxX = Math.max(this.maxX, x);
    this.maxY = Math.max(this.maxY, y);
  }
  updateCurvePathMinMax(transform, x0, y0, x1, y1, x2, y2, x3, y3) {
    const box = Util.bezierBoundingBox(x0, y0, x1, y1, x2, y2, x3, y3);
    this.updatePathMinMax(transform, box[0], box[1]);
    this.updatePathMinMax(transform, box[2], box[3]);
  }
  getPathBoundingBox() {
    return [this.minX, this.minY, this.maxX, this.maxY];
  }
  updateClipFromPath() {
    const intersect = Util.intersect(this.clipBox, this.getPathBoundingBox());
    this.startNewPathAndClipBox(intersect || [0, 0, 0, 0]);
  }
  startNewPathAndClipBox(box) {
    this.clipBox = box;
    this.minX = Infinity;
    this.minY = Infinity;
    this.maxX = 0;
    this.maxY = 0;
  }
  getClippedPathBoundingBox() {
    return Util.intersect(this.clipBox, this.getPathBoundingBox());
  }
}
function putBinaryImageData(ctx, imgData, transferMaps = null) {