Link to PDF file (or attach file here):
[pages4.pdf](https://github.com/mozilla/pdf.js/files/1128300/pages4.pdf)

Configuration:
- Web browser and its version: Firefox 54
- Operating system and its version: Win 10
- PDF.js version: 1.8.522
- Is an extension: no

What is the expected behavior? (add screenshot)
![chrome1-1 1](https://user-images.githubusercontent.com/146436/27918380-2f74512a-6245-11e7-8525-d0038fa6c2e8.jpg)
![chrome1-2 1](https://user-images.githubusercontent.com/146436/27918425-54f8e47e-6245-11e7-9bff-127f79ad0511.jpg)


What went wrong? (add screenshot)
![screenshot from 2017-07-06 12-10-30](https://user-images.githubusercontent.com/146436/27918442-5d57624e-6245-11e7-9436-5ba31cc8bd1a.png)
![screenshot from 2017-07-06 12-10-44](https://user-images.githubusercontent.com/146436/27918454-63b486da-6245-11e7-9eb5-c03aa5c40943.png)



const transform = this.ctx.mozCurrentTransform;
    return [
      transform[0] * x + transform[2] * y + transform[4],
      transform[1] * x + transform[3] * y + transform[5],
    ];
  }
  isContentVisible() {
    for (let i = this.markedContentStack.length - 1; i >= 0; i--) {
      if (!this.markedContentStack[i].visible) {
        return false;
      }
    }
    return true;
  }
}
for (const op in OPS) {
  if (CanvasGraphics.prototype[op] !== undefined) {
    CanvasGraphics.prototype[OPS[op]] = CanvasGraphics.prototype[op];
  }
}
export { CanvasGraphics };