Test for bug 110993 : ImageDocument 's incorrect zoom behavior.

1. Open this image link on your browser. resources/200x200.png
2. Make the browser window(rendering area)'s height and width about 3 times bigger than the image.
3. Zoom in several times until the image gets bigger than the browser window using keyboard shortcut (e.g., ctrl + '+' in Linux Chrome)
4. Zoom back to the original state (100%) using keyboard shortcut (e.g., ctrl + '-' in Linux Chrome)
5. If the image size is 200x200, pass, otherwise, fail.