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)



unreachable("Should not call beginImageData");
  }
  paintFormXObjectBegin(matrix, bbox) {
    if (!this.contentVisible) {
      return;
    }
    this.save();
    this.baseTransformStack.push(this.baseTransform);
    if (Array.isArray(matrix) && matrix.length === 6) {
      this.transform.apply(this, matrix);
    }
    this.baseTransform = this.ctx.mozCurrentTransform;
    if (bbox) {
      const width = bbox[2] - bbox[0];
      const height = bbox[3] - bbox[1];
      this.ctx.rect(bbox[0], bbox[1], width, height);
      this.clip();
      this.endPath();
    }
  }
  paintFormXObjectEnd() {
    if (!this.contentVisible) {
      return;
    }
    this.restore();
    this.baseTransform = this.baseTransformStack.pop();
  }
  beginGroup(group) {