Attach (recommended) or Link to PDF file here: https://www.recom-power.com/pdf/Powerline-AC-DC/RAC05-K.pdf

Configuration:
- Web browser and its version: Firefox 56.0 (64-bit)
- Operating system and its version: Windows 10 with OS Build 15063.632
- PDF.js version: ?
- Is an extension: Built-in

Steps to reproduce the problem:
1. Open Page

What is the expected behavior? To properly render the first page. 
![image](https://user-images.githubusercontent.com/1151969/31415345-b1504022-add7-11e7-855b-8030a308f7a2.png)

What went wrong? Renders poorly.
![image](https://user-images.githubusercontent.com/1151969/31415363-d8842096-add7-11e7-818d-728c1102891b.png)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension): ?

if (hasBackdrop) {
      composeSMaskBackdrop(maskData.data, r0, g0, b0);
    }
    composeFn(maskData.data, layerData.data, transferMap);
    maskCtx.putImageData(layerData, 0, row);
  }
}
function composeSMask(ctx, smask, layerCtx) {
  const mask = smask.canvas;
  const maskCtx = smask.context;
  ctx.setTransform(
    smask.scaleX,
    0,
    0,
    smask.scaleY,
    smask.offsetX,
    smask.offsetY
  );
  genericComposeSMask(
    maskCtx,
    layerCtx,
    mask.width,
    mask.height,
    smask.subtype,
    smask.backdrop,
    smask.transferMap
  );
  ctx.drawImage(mask, 0, 0);
}
function getImageSmoothingEnabled(transform, interpolate) {