Check padding values for content view (white area)

TreeView wrapper was changed to a CssLayout and hijacked CSS rule used by other view wrappers.

Perhaps turn Thumbnail/ListView wrappers to CssLayouts as well. (See Layout Guidelines https://docs.google.com/document/d/1xaDbdbPFhfII6c2RF41axhBK4Sft7PEIW_q80k3bmM0/edit)