The color setting was picked from SplitWindow::Paint()
for visual consistency with the sizers used in Impress
for example.

This commit also resurects presumably dead code.
In fact GDB let me see that only the short path
was taken.

This has an impact on Calc's window splitters and
on more visibly on the basic IDE which now looks
much nicer :)

EDITS:
 restricted this commit impact to IDE as a poc

Change-Id: I9a051fd894feccff4bbc7db7efe1160cb2c3a2c6