Attach (recommended) or Link to PDF file here:
[shading_pattern.pdf](https://github.com/mozilla/pdf.js/files/1532598/shading_pattern.pdf)

Configuration:
- Web browser and its version: Firefox 57.0
- Operating system and its version: Debian GNU/Linux 9 64-bit
- PDF.js version: tried with Firefox's 1.9.583 and with online viewer 2.0.185
- Is a browser extension: no

Steps to reproduce the problem:
1. Open the attached file with the online viewer https://mozilla.github.io/pdf.js/web/viewer.html

What is the expected behavior? (add screenshot)
![image](https://user-images.githubusercontent.com/11061462/33626267-d9a57dee-d9d8-11e7-8712-cfa17c038259.png)
(Image captured from Adobe Reader CS.) The shading needs to be inside the letters.

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/11061462/33626285-eaabd462-d9d8-11e7-94e2-96480b57750d.png)
The shading seems to be displaced and upside-down, for it does not cover all the characters of the word.

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

if (isNum(glyph)) {
        spacingLength = (spacingDir * glyph * fontSize) / 1000;
        this.ctx.translate(spacingLength, 0);
        current.x += spacingLength * textHScale;
        continue;
      }
      const spacing = (glyph.isSpace ? wordSpacing : 0) + charSpacing;
      const operatorList = font.charProcOperatorList[glyph.operatorListId];
      if (!operatorList) {
        warn(`Type3 character "${glyph.operatorListId}" is not available.`);
        continue;
      }
      if (this.contentVisible) {
        this.processingType3 = glyph;
        this.save();
        ctx.scale(fontSize, fontSize);
        ctx.transform.apply(ctx, fontMatrix);
        this.executeOperatorList(operatorList);
        this.restore();
      }
      const transformed = Util.applyTransform([glyph.width, 0], fontMatrix);
      width = transformed[0] * fontSize + spacing;
      ctx.translate(width, 0);
      current.x += width * textHScale;
    }
    ctx.restore();
    this.processingType3 = null;
  }
  
  setCharWidth(xWidth, yWidth) {