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!
const { context: ctx } = this.cachedCanvases.getCanvas(
      "isFontSubpixelAAEnabled",
      10,
      10
    );
    ctx.scale(1.5, 1);
    ctx.fillText("I", 0, 10);
    const data = ctx.getImageData(0, 0, 10, 10).data;
    let enabled = false;
    for (let i = 3; i < data.length; i += 4) {
      if (data[i] > 0 && data[i] < 255) {
        enabled = true;
        break;
      }
    }
    return shadow(this, "isFontSubpixelAAEnabled", enabled);
  }
  showText(glyphs) {