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
MApplicationElement element = modelService.find(id, getContainer());
		if (element instanceof MPlaceholder) {
			((MPlaceholder) element).getRef().setCurSharedRef((MPlaceholder) element);
			element = ((MPlaceholder) element).getRef();
		}
		return element instanceof MPart ? (MPart) element : null;
	}
	public Collection<MPart> getParts() {
		return modelService.findElements(getContainer(), null, MPart.class, null);
	}
	public boolean isPartVisible(MPart part) {
		if (isInContainer(part)) {
			MUIElement element = part;
			MElementContainer<?> parent = part.getParent();
			if (parent == null) {
				
				element = part.getCurSharedRef();
				if (element == null) {
					return false;
				}
				parent = element.getParent();
				if (parent == null) {
					return false;
				}
			}
			if (parent instanceof MPartStack) {
				return parent.getSelectedElement() == element;
			}
			return element.isVisible();
		}