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):

ctx.clip = function ctxRotate(rule) {
    destCtx.clip(rule);
    this.__originalClip(rule);
  };
  ctx.moveTo = function (x, y) {
    destCtx.moveTo(x, y);
    this.__originalMoveTo(x, y);
  };
  ctx.lineTo = function (x, y) {
    destCtx.lineTo(x, y);
    this.__originalLineTo(x, y);
  };
  ctx.bezierCurveTo = function (cp1x, cp1y, cp2x, cp2y, x, y) {
    destCtx.bezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y);
    this.__originalBezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y);
  };
  ctx.rect = function (x, y, width, height) {
    destCtx.rect(x, y, width, height);
    this.__originalRect(x, y, width, height);
  };
  ctx.closePath = function () {
    destCtx.closePath();
    this.__originalClosePath();
  };
  ctx.beginPath = function () {
    destCtx.beginPath();
    this.__originalBeginPath();
  };
}
function addContextCurrentTransform(ctx) {