Bug 63420 [R21PRES] Flash on tab switch
bundles/org.eclipse.ui.presentations.r21/src/org/eclipse/ui/internal/presentations/R21EditorStackPresentation.java
private Listener resizeListener = new Listener() {
		public void handleEvent(Event e) {
			setControlSize();
		}
	};
	
	private IPropertyListener childPropertyChangeListener = new IPropertyListener() {
		public void propertyChanged(Object source, int property) {
			if (source instanceof IPresentablePart) {
				IPresentablePart part = (IPresentablePart) source;
				childPropertyChanged(part, property);
			}
		}
	};
	
	private DisposeListener tabDisposeListener = new DisposeListener() {
		public void widgetDisposed(DisposeEvent e) {
			if (e.widget instanceof CTabItem) {
				CTabItem item = (CTabItem) e.widget;
				IPresentablePart part = getPartForTab(item);
				part.removePropertyListener(childPropertyChangeListener);
			}
		}
	};
	
	private ShellAdapter shellListener = new ShellAdapter() {
		public void shellActivated(ShellEvent event) {
			updateGradient();
		}
		public void shellDeactivated(ShellEvent event) {