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.lineX = 0;
    this.lineY = 0;
    
    this.charSpacing = 0;
    this.wordSpacing = 0;
    this.textHScale = 1;
    this.textRenderingMode = TextRenderingMode.FILL;
    this.textRise = 0;
    
    this.fillColor = "#000000";
    this.strokeColor = "#000000";
    this.patternFill = false;
    
    this.fillAlpha = 1;
    this.strokeAlpha = 1;
    this.lineWidth = 1;
    this.activeSMask = null;
    this.transferMaps = null;
    this.startNewPathAndClipBox([0, 0, width, height]);
  }
  clone() {
    const clone = Object.create(this);
    clone.clipBox = this.clipBox.slice();
    return clone;
  }
  setCurrentPoint(x, y) {
    this.x = x;
    this.y = y;
  }
  updatePathMinMax(transform, x, y) {