Spark TitleWindow without optional titleDisplay skin part positions the close button oddly

Found in 4.0.0 (build 13963)

Steps to reproduce:
1. Compile and run attached MXML file.
2. Note the placement of the TitleWindow close button vs TitleWindow title bar area.

Actual Results:
Close button is positioned too low in the header.

Expected Results:
Close button should be centered vertically.

Workaround (if any):
Adjust the close button's position in the custom skin.
Me thinks the issue is that without the title bar text, the header isnt as tall as it is when the titleDisplay is present, thus requiring us to tweak the close button constraints.