Bug 65444 [R21PRES] Close button shown when views not closeable
RC1 build - run the browser example using the R2.1 presentation - the views have close buttons in the titlebar, but should not because the perspective has fixed="true" (meaning that all initial views are non-moveable and non-closeable)
bundles/org.eclipse.ui.presentations.r21/src/org/eclipse/ui/internal/presentations/R21BasicStackPresentation.java
* 
	 * @return the current toolbar or null if none
	 */
	protected Control getCurrentToolbar() {
		IPresentablePart part = getCurrentPart();		
		if (part == null) {
			return null;
		}
		return part.getToolBar();
	}
	
	/* (non-Javadoc)
	 * @see org.eclipse.ui.presentations.StackPresentation#showSystemMenu()
	 */
	public void showSystemMenu() {
		IPresentablePart part = getCurrentPart();
		if (part != null) {
			Rectangle bounds = DragUtil.getDisplayBounds(paneFolder.getControl());
			
			int idx = paneFolder.getSelectionIndex();
			if (idx > -1) {
				CTabItem item = paneFolder.getItem(idx);
				Rectangle itemBounds = item.getBounds();
				
				bounds.x += itemBounds.x;
				bounds.y += itemBounds.y;
			}
			
			Point location = new Point(bounds.x, bounds.y + paneFolder.getTabHeight());
			showSystemMenu(location);