Bug 327964 EPartService's hidePart may fail when trying to hide a shared part that's in a shared container
The placeholder retrieval code in the EPartService implementation doesn't go far down deep enough and actually stops at the shared container level. This causes the placeholder of the shared part to not be found.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
application.setSelectedElement(window);
		MPerspectiveStack perspectiveStack = AdvancedFactoryImpl.eINSTANCE
				.createPerspectiveStack();
		window.getChildren().add(perspectiveStack);
		window.setSelectedElement(perspectiveStack);
		MPerspective perspective = AdvancedFactoryImpl.eINSTANCE
				.createPerspective();
		perspectiveStack.getChildren().add(perspective);
		perspectiveStack.setSelectedElement(perspective);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = window.getContext().get(EPartService.class);
		MPlaceholder placeholder = partService.createSharedPart("partId", true);
		MPart sharedPart = (MPart) placeholder.getRef();
		sharedPart.setCurSharedRef(placeholder);
		placeholder.setToBeRendered(false);
		sharedPart.setToBeRendered(false);
		perspective.getChildren().add(placeholder);
		partService.showPart(sharedPart, partState);
		assertNotNull(perspective.getSelectedElement());
		assertEquals(placeholder, perspective.getSelectedElement());
	}
	public void testShowPart_Bug322368_Placeholder_ACTIVATE() {
		testShowPart_Bug322368_Placeholder(PartState.ACTIVATE);
	}
	public void testShowPart_Bug322368_Placeholder_VISIBLE() {
		testShowPart_Bug322368_Placeholder(PartState.VISIBLE);
	}
	public void testShowPart_Bug322368_Placeholder_CREATE() {
		testShowPart_Bug322368_Placeholder(PartState.CREATE);