Link to PDF file (or attach file here):
https://issues.apache.org/jira/secure/attachment/12650283/000004_ShadingPatternTextPDF.pdf

Configuration:
- Web browser and its version: FF 51.0.1 32bit
- Operating system and its version: W7
- PDF.js version: latest

Steps to reproduce the problem:
display file

What is the expected behavior? (add screenshot)
![ok](https://cloud.githubusercontent.com/assets/6665575/23339534/5ff2de9c-fc25-11e6-837e-0fdaf81b4ca9.png)

What went wrong? (add screenshot)
![nok](https://cloud.githubusercontent.com/assets/6665575/23339536/63f7a37e-fc25-11e6-813c-cc218cc4def3.png)

possibly similar problem:
https://www.pdflib.com/fileadmin/pdflib/Cookbook/pdf/color_gradient.pdf (shaded text completely missing)
https://issues.apache.org/jira/secure/attachment/12630566/pslib-shading.pdf (page 4, part of text missing)
https://issues.apache.org/jira/secure/attachment/12652009/pattern-shading-2-4-idMatrix.pdf (some text missing)
https://issues.apache.org/jira/secure/attachment/12652010/pattern-shading-2-4-noMatrix.pdf (some text missing)

0,
      scaled.img.width,
      scaled.img.height,
      0,
      0,
      width,
      height
    );
    fillCtx.globalCompositeOperation = "source-in";
    const inverse = Util.transform(fillCtx.mozCurrentTransformInverse, [
      1,
      0,
      0,
      1,
      -offsetX,
      -offsetY,
    ]);
    fillCtx.fillStyle = isPatternFill
      ? fillColor.getPattern(ctx, this, inverse, false)
      : fillColor;
    fillCtx.fillRect(0, 0, width, height);
    
    return {
      canvas: fillCanvas.canvas,
      offsetX: Math.round(offsetX),
      offsetY: Math.round(offsetY),
    };
  }
  
  setLineWidth(width) {