BUG 1087015: Demos - popup

Added the demo studio style sheet to the pop up to change the background color to be white.

This introduced a few problems which I then tried to correct. (box-shadow and margins).

Couldn't test locally, tested by adding compiled local style sheet to the popup on production.
Merge pull request #2912 from stephaniehobson/BUG-1087015-demos-popup

BUG 1087015: Demos - popup