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)



ctx.strokeStyle = "#000000";
  ctx.fillStyle = "#000000";
  ctx.fillRule = "nonzero";
  ctx.globalAlpha = 1;
  ctx.lineWidth = 1;
  ctx.lineCap = "butt";
  ctx.lineJoin = "miter";
  ctx.miterLimit = 10;
  ctx.globalCompositeOperation = "source-over";
  ctx.font = "10px sans-serif";
  if (ctx.setLineDash !== undefined) {
    ctx.setLineDash([]);
    ctx.lineDashOffset = 0;
  }
}
function composeSMaskBackdrop(bytes, r0, g0, b0) {