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 = img.width;
    const height = img.height;
    let widthScale = Math.max(
      Math.hypot(inverseTransform[0], inverseTransform[1]),
      1
    );
    let heightScale = Math.max(
      Math.hypot(inverseTransform[2], inverseTransform[3]),
      1
    );
    let paintWidth = width,
      paintHeight = height;
    let tmpCanvasId = "prescale1";
    let tmpCanvas, tmpCtx;
    while (
      (widthScale > 2 && paintWidth > 1) ||
      (heightScale > 2 && paintHeight > 1)
    ) {
      let newWidth = paintWidth,
        newHeight = paintHeight;
      if (widthScale > 2 && paintWidth > 1) {
        newWidth = Math.ceil(paintWidth / 2);
        widthScale /= paintWidth / newWidth;