Bug 63420 [R21PRES] Flash on tab switch
bundles/org.eclipse.ui.presentations.r21/src/org/eclipse/ui/internal/presentations/R21EditorStackPresentation.java
PresentationUtil.removeDragListener(tabFolder, dragListener);
		
		systemMenuManager.dispose();
		systemMenuManager.removeAll();
		
		tabFolder.dispose();
		tabFolder = null;
	}
	
	private int activeState = AS_INACTIVE;
	/**
	 * Update the tab folder's colours to match the current theme settings and
	 * active state
	 */
	private void updateGradient() {
		if (isDisposed())
			return;
		Color fgColor;
		Color[] bgColors;
		int[] bgPercents;
		boolean vertical = false;
		if (activeState == AS_ACTIVE_FOCUS) {
			if (getShellActivated()) {
				fgColor = R21Colors.getSystemColor(SWT.COLOR_TITLE_FOREGROUND);
				bgColors = R21Colors.getActiveEditorGradient();
				bgPercents = R21Colors.getActiveEditorGradientPercents();
			} else {
				fgColor = R21Colors
						.getSystemColor(SWT.COLOR_TITLE_INACTIVE_FOREGROUND);
				bgColors = R21Colors.getDeactivatedEditorGradient();