a) expand to fit the available space
b) make the controls and the preview the same size
c) reorganize the three options of color, gradient and bitmap to all put the
preview in the same place and adjust so the preview is the same size in each
case, i.e. switching between views gives the impression of a single shared
preview element
d) put a border around the gradient list so its area is visually noticable
to be the same size as its preview area

Change-Id: I88735778bb482f9dd011f890d170be127877367a