Clean up more Quicksand
Summary: Creates a background that renders inside the Quicksand frame, through sorcery.
Test Plan: Turn on Quicksand, visit lots of pages. See correct background colors. This probably blows something up I'm not testing.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D16642