private void rotateRight( Rectangle viewR, Rectangle r ) {
		int x = viewR.x + (viewR.width - (r.y + r.height));
		int y = viewR.y + r.x;
		r.setBounds( x, y, r.height, r.width );
	}
Actually does nearly the same as super.paintContentBorder() but
  - not using UIManager.getColor("TabbedPane.contentAreaColor") to be GUI builder friendly
  - tabsOverlapBorder is always true
  - paint full border (if enabled)
  - not invoking paintContentBorder*Edge() methods
  - repaint selection
  - painting active tab border style
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatTabbedPaneUI.java