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)

const width = canvas.width;
      const height = canvas.height;
      const bl = Util.applyTransform([0, 0], inv);
      const br = Util.applyTransform([0, height], inv);
      const ul = Util.applyTransform([width, 0], inv);
      const ur = Util.applyTransform([width, height], inv);
      const x0 = Math.min(bl[0], br[0], ul[0], ur[0]);
      const y0 = Math.min(bl[1], br[1], ul[1], ur[1]);
      const x1 = Math.max(bl[0], br[0], ul[0], ur[0]);
      const y1 = Math.max(bl[1], br[1], ul[1], ur[1]);
      this.ctx.fillRect(x0, y0, x1 - x0, y1 - y0);
    } else {
      
      
      
      
      
      this.ctx.fillRect(-1e10, -1e10, 2e10, 2e10);
    }
    this.compose(this.current.getClippedPathBoundingBox());
    this.restore();
  }
  
  beginInlineImage() {
    unreachable("Should not call beginInlineImage");
  }
  beginImageData() {
    unreachable("Should not call beginImageData");
  }
  paintFormXObjectBegin(matrix, bbox) {