PIVOT-955, last components updated to handle the themeIsFlat.
Note that here the Background color is drawn only in flat mode (because it wasn't drawn before in the normal, non-flat mode, so the old behavior is respected).

git-svn-id: https://svn.apache.org/repos/asf/pivot/trunk@1615935 13f79535-47bb-0310-9956-ffa450edef68