Bug 63420 [R21PRES] Flash on tab switch
bundles/org.eclipse.ui.presentations.r21/src/org/eclipse/ui/internal/presentations/R21BasicStackPresentation.java
* @see org.eclipse.ui.internal.skins.Presentation#setActive(boolean)
	 */
	public void setActive(boolean isActive) {
		activeState = isActive;
		updateGradient();
	}
	/**
	 * Return whether the window's shell is activated
	 */
	boolean getShellActivated() {
		return shellActive;
	}
	/**
	 * Returns the top level window.
	 */
	public Window getWindow() {
		Control ctrl = getControl();
		if (ctrl != null) {
			Object data = ctrl.getShell().getData();
			if (data instanceof Window)
				return (Window) data;
		}
		return null;
	}
	private CTabItem createPartTab(IPresentablePart part, int tabIndex) {
		CTabItem tabItem;
		int style = SWT.NONE;
		if (getSite().isCloseable(part))
			style |= SWT.CLOSE;
		tabItem = paneFolder.createItem(style, tabIndex);