Bug 327820 Active part stack is not highlighted in a newly opened perspective
1. Run on a new workspace. 2. Activate the 'Outline' view. 3. Window > Open Perspective > Debug 4. The 'Outline' view is active but its tab folder is not coloured blue.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartServiceImpl.java
public void switchPerspective(MPerspective perspective) {
		Assert.isNotNull(perspective);
		MWindow window = getWindow();
		if (window != null && isInContainer(window, perspective)) {
			perspective.getParent().setSelectedElement(perspective);
			List<MPart> newPerspectiveParts = modelService.findElements(perspective, null,
					MPart.class, null);
			
			if (newPerspectiveParts.contains(activePart)
					&& partActivationHistory.isValid(perspective, activePart)) {
				MPart target = activePart;
				IEclipseContext activeChild = activePart.getContext().getParent().getActiveChild();
				if (activeChild != null) {
					activeChild.deactivate();
					perspective.getContext().activate();
				}
				modelService.bringToTop(target);
				partActivationHistory.activate(target, false);
				return;
			}
			MPart newActivePart = perspective.getContext().getActiveLeaf().get(MPart.class);
			if (newActivePart == null) {
				
				MPart candidate = partActivationHistory.getActivationCandidate(perspective);
				if (candidate != null) {
					modelService.bringToTop(candidate);
					partActivationHistory.activate(candidate, false);
					return;
				}
			}