Bug 327044 EPartService's hidePart(*) should unset the part's parent element if the part is the selected element
It is not valid to have a selected element that's TBR flag is 'false'.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
List<MPart> partsB = modelService.findElements(perspectiveB,
				part.getElementId(), MPart.class, null);
		assertEquals(0, partsB.size());
		List<MPlaceholder> placeholdersB = modelService.findElements(
				perspectiveB, part.getElementId(), MPlaceholder.class, null);
		assertEquals(0, placeholdersB.size());
		perspectiveStack.setSelectedElement(perspectiveB);
		window.getContext().set(IContextConstants.ACTIVE_CHILD,
				perspectiveB.getContext());
		partService.showPart(part, PartState.ACTIVATE);
		partsA = modelService.findElements(perspectiveA, part.getElementId(),
				MPart.class, null);
		assertEquals(1, partsA.size());
		assertEquals(part, partsA.get(0));
		placeholdersA = modelService.findElements(perspectiveA,
				part.getElementId(), MPlaceholder.class, null);
		assertEquals(1, placeholdersA.size());
		assertEquals(part, placeholdersA.get(0).getRef());
		partsB = modelService.findElements(perspectiveB, part.getElementId(),
				MPart.class, null);
		assertEquals(1, partsB.size());
		assertEquals(part, partsB.get(0));
		placeholdersB = modelService.findElements(perspectiveB,
				part.getElementId(), MPlaceholder.class, null);
		assertEquals(1, placeholdersB.size());
		assertEquals(part.getCurSharedRef(), placeholdersB.get(0));
	}
	public void testShowPart_Bug320578_E() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();