Show a preview of the selected font size immediately (WIP)

Modified the font size preference dialog to show the user the selected
font size immediately. Also split the size description and percentage on
their own lines to show a preview of two different font sizes. In
addition, removed the gigantic title bar from the dialog.

Change-Id: Ifc1e930f9420bde0bb6fd61b1a395c3d36b4fb0b