Bug 328946 Part activation history may return incorrect candidate if no placeholders could be found in a perspective
1. Window > Open Perspective > Other... > CVS Repository Exploring 2. Hide the 'CVS Repositories' view. 3. The 'History' view should become active, it is not.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartServiceImpl.java
if (parent == null) {
					return false;
				}
			}
			if (parent instanceof MPartStack) {
				return parent.getSelectedElement() == element;
			}
			return element.isVisible();
		}
		return false;
	}
	private boolean isInContainer(MUIElement element) {
		return isInContainer(getContainer(), element);
	}
	boolean isInContainer(MElementContainer<?> container, MUIElement element) {
		for (Object object : container.getChildren()) {
			if (object == element) {
				return true;
			} else if (object instanceof MElementContainer<?>) {
				if (isInContainer((MElementContainer<?>) object, element)) {
					return true;
				}
			} else if (object instanceof MPlaceholder) {
				MUIElement ref = ((MPlaceholder) object).getRef();
				if (ref == element) {
					return true;
				} else if (ref instanceof MElementContainer<?>) {
					if (isInContainer((MElementContainer<?>) ref, element)) {
						return true;
					}