Link to PDF file (or attach file here):
[RP_25884_V2_UEL Semi Finals 2016-17_concepts.pdf](https://github.com/mozilla/pdf.js/files/994423/RP_25884_V2_UEL.Semi.Finals.2016-17_concepts.pdf)

Configuration:
- Web browser and its version: Chrome 58, Firefox 53
- Operating system and its version: MacOS 10.11.6
- PDF.js version:
- Is an extension: No

Steps to reproduce the problem:
1.  View the file the file


What is the expected behavior? (add screenshot)
<img width="560" alt="screen shot 2017-05-11 at 2 06 36 pm" src="https://cloud.githubusercontent.com/assets/2474027/25971992/189f4ebe-3653-11e7-8847-c9011984cb8d.png">

What went wrong? (add screenshot)
Textlayer exists here but font fails to render. No warning in the console from what I can see. Maybe related to the gradient?

<img width="637" alt="screen shot 2017-05-11 at 2 06 20 pm" src="https://cloud.githubusercontent.com/assets/2474027/25971997/1b518cc6-3653-11e7-96c0-9a03ffcb7d6e.png">

Thanks!
_createMaskCanvas(img) {
    const ctx = this.ctx;
    const width = img.width,
      height = img.height;
    const fillColor = this.current.fillColor;
    const isPatternFill = this.current.patternFill;
    const maskCanvas = this.cachedCanvases.getCanvas(
      "maskCanvas",
      width,
      height
    );
    const maskCtx = maskCanvas.context;
    putBinaryImageMask(maskCtx, img);
    
    
    
    
    const objToCanvas = ctx.mozCurrentTransform;
    let maskToCanvas = Util.transform(objToCanvas, [
      1 / width,
      0,
      0,
      -1 / height,
      0,
      0,
    ]);
    maskToCanvas = Util.transform(maskToCanvas, [1, 0, 0, 1, 0, -height]);
    const cord1 = Util.applyTransform([0, 0], maskToCanvas);
    const cord2 = Util.applyTransform([width, height], maskToCanvas);
    const rect = Util.normalizeRect([cord1[0], cord1[1], cord2[0], cord2[1]]);