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)

this.save();
    if (this.baseTransform) {
      this.ctx.setTransform.apply(this.ctx, this.baseTransform);
    }
  }
  endAnnotations() {
    this.restore();
  }
  beginAnnotation(id, rect, transform, matrix) {
    this.save();
    resetCtxToDefault(this.ctx);
    this.current = new CanvasExtraState(
      this.ctx.canvas.width,
      this.ctx.canvas.height
    );
    if (Array.isArray(rect) && rect.length === 4) {
      const width = rect[2] - rect[0];
      const height = rect[3] - rect[1];
      this.ctx.rect(rect[0], rect[1], width, height);
      this.clip();
      this.endPath();
    }
    this.transform.apply(this, transform);
    this.transform.apply(this, matrix);
  }
  endAnnotation() {
    this.restore();
  }
  paintImageMaskXObject(img) {