Forcing GPU mode for better CSS Filter rendering on Retina.

This is a fix for #9377.

Scrolling is better now for some reason. (Possible fix for #9486?)
@larz0 I'm curious why this particular SVG file (and we have many) renders more crisp with GPU enabled?  Is there something about this image that's different?  

Doing this effectively turns on hardware compositing for the entire page (making all compositing on the GPU and, thus, seemingly faster) so wouldn't it be logical and more readable to add the Null Transform Hack on the body style?