Bug 337002 EPartService leaks previously active part
A reference is kept to the previously active part. This is unnecessary. We only need it to fire events. After the deactivation events have been fired, we should no longer need to keep it lying around.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartServiceImpl.java
private MElementContainer<MUIElement> getParent(MUIElement element) {
		MElementContainer<MUIElement> parent = element.getParent();
		if (parent == null) {
			MPlaceholder placeholder = element.getCurSharedRef();
			if (placeholder == null) {
				MElementContainer<MUIElement> container = getContainer();
				return findContainer(container, element);
			}
			return placeholder.getParent();
		}
		return parent;
	}
	private MElementContainer<MUIElement> findContainer(MElementContainer<?> container,
			MUIElement element) {
		for (Object child : container.getChildren()) {
			if (child == element) {
				return (MElementContainer<MUIElement>) container;
			} else if (child instanceof MPlaceholder) {
				MPlaceholder placeholder = (MPlaceholder) child;
				MUIElement ref = placeholder.getRef();
				if (ref == element) {
					return (MElementContainer<MUIElement>) container;
				} else if (ref instanceof MElementContainer<?>) {
					MElementContainer<MUIElement> match = findContainer((MElementContainer<?>) ref,
							element);
					if (match != null) {
						return match;
					}
				}
			} else if (child instanceof MElementContainer<?>) {