Bug 327980 Part activation history should not be perspective-dependent
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartActivationHistory.java
perspectiveActivationHistories.clear();
	}
	void activate(MPart part, boolean activateBranch) {
		IEclipseContext context = part.getContext();
		if (activateBranch) {
			context.activateBranch();
		} else {
			IEclipseContext parent = context.getParent();
			do {
				context.activate();
				context = parent;
				parent = parent.getParent();
			} while (parent.get(MWindow.class) != null);
		}
		LinkedList<MPart> perspectiveActivationHistory = getPerspectiveActivationHistory(part);
		if (perspectiveActivationHistory != null) {
			perspectiveActivationHistory.remove(part);
			perspectiveActivationHistory.addFirst(part);
		}
		generalActivationHistory.remove(part);
		generalActivationHistory.addFirst(part);
	}
	/**
	 * Checks to see if this element and its parents are actually being rendered.
	 */
	private boolean isValid(MUIElement element) {
		if (element == null) {
			return false;
		}
		if (element instanceof MApplication) {