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):

matrix = Util.transform(matrix, owner.baseTransform);
      if (this.matrix) {
        matrix = Util.transform(matrix, this.matrix);
      }
    }
    const temporaryPatternCanvas = this.createPatternCanvas(owner);
    let domMatrix = new DOMMatrix(matrix);
    
    
    domMatrix = domMatrix.translate(
      temporaryPatternCanvas.offsetX,
      temporaryPatternCanvas.offsetY
    );
    domMatrix = domMatrix.scale(
      1 / temporaryPatternCanvas.scaleX,
      1 / temporaryPatternCanvas.scaleY
    );
    const pattern = ctx.createPattern(temporaryPatternCanvas.canvas, "repeat");
    try {
      pattern.setTransform(domMatrix);
    } catch (ex) {
      
      
      warn(`TilingPattern.getPattern: "${ex?.message}".`);
    }
    return pattern;
  }
}
export { getShadingPattern, TilingPattern };