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)

maskCtx,
            this,
            ctx.mozCurrentTransformInverse,
            false
          )
        : fillColor;
      maskCtx.fillRect(0, 0, width, height);
      maskCtx.restore();
      ctx.save();
      ctx.transform.apply(ctx, image.transform);
      ctx.scale(1, -1);
      ctx.drawImage(maskCanvas.canvas, 0, 0, width, height, 0, -1, 1, 1);
      ctx.restore();
    }
    this.compose();
  }
  paintImageXObject(objId) {
    if (!this.contentVisible) {
      return;
    }
    const imgData = objId.startsWith("g_")
      ? this.commonObjs.get(objId)
      : this.objs.get(objId);
    if (!imgData) {
      warn("Dependent image isn't ready yet");
      return;
    }
    this.paintInlineImageXObject(imgData);
  }
  paintImageXObjectRepeat(objId, scaleX, scaleY, positions) {