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 (!this.contentVisible) {
      return;
    }
    const width = imgData.width;
    const height = imgData.height;
    const ctx = this.ctx;
    this.save();
    
    ctx.scale(1 / width, -1 / height);
    let imgToPaint;
    
    if (
      (typeof HTMLElement === "function" && imgData instanceof HTMLElement) ||
      !imgData.data
    ) {
      imgToPaint = imgData;
    } else {
      const tmpCanvas = this.cachedCanvases.getCanvas(
        "inlineImage",
        width,
        height
      );
      const tmpCtx = tmpCanvas.context;
      putBinaryImageData(tmpCtx, imgData, this.current.transferMaps);
      imgToPaint = tmpCanvas.canvas;
    }