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 tmpCtx = tmpCanvas.context;
    const data = tmpCtx.createImageData(width, height);
    if (backgroundColor) {
      const bytes = data.data;
      for (let i = 0, ii = bytes.length; i < ii; i += 4) {
        bytes[i] = backgroundColor[0];
        bytes[i + 1] = backgroundColor[1];
        bytes[i + 2] = backgroundColor[2];
        bytes[i + 3] = 255;
      }
    }
    for (const figure of this._figures) {
      drawFigure(data, figure, context);
    }
    tmpCtx.putImageData(data, BORDER_SIZE, BORDER_SIZE);
    const canvas = tmpCanvas.canvas;
    return {
      canvas,
      offsetX: offsetX - BORDER_SIZE * scaleX,
      offsetY: offsetY - BORDER_SIZE * scaleY,
      scaleX,
      scaleY,
    };
  }
  getPattern(ctx, owner, inverse, shadingFill = false) {
    applyBoundingBox(ctx, this._bbox);
    let scale;
    if (shadingFill) {
      scale = Util.singularValueDecompose2dScale(ctx.mozCurrentTransform);