Layout.DynamicBackground: Allow CSS overrides
Layout.DynamicBackground: Allow CSS overrides

Previously the dynamic background would have overridden the CSS
overrides.

https://phabricator.endlessm.com/T16822

endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib