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)

m[1] * c + m[3] * d,
      m[0] * e + m[2] * f + m[4],
      m[1] * e + m[3] * f + m[5],
    ];
    ctx._originalTransform(a, b, c, d, e, f);
  };
  ctx.setTransform = function ctxSetTransform(a, b, c, d, e, f) {
    this._transformMatrix = [a, b, c, d, e, f];
    ctx._originalSetTransform(a, b, c, d, e, f);
  };
  ctx.resetTransform = function ctxResetTransform() {
    this._transformMatrix = [1, 0, 0, 1, 0, 0];
    ctx._originalResetTransform();
  };
  ctx.rotate = function ctxRotate(angle) {
    const cosValue = Math.cos(angle);
    const sinValue = Math.sin(angle);
    const m = this._transformMatrix;
    this._transformMatrix = [
      m[0] * cosValue + m[2] * sinValue,
      m[1] * cosValue + m[3] * sinValue,
      m[0] * -sinValue + m[2] * cosValue,
      m[1] * -sinValue + m[3] * cosValue,
      m[4],
      m[5],
    ];
    this._originalRotate(angle);
  };
}
class CachedCanvases {