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
stack.getChildren().add(partB);
		stack.setSelectedElement(partA);
		initialize(applicationContext, application);
		getEngine().createGui(windowA);
		getEngine().createGui(windowB);
		EPartService partServiceA = (EPartService) windowA.getContext().get(
				EPartService.class.getName());
		EPartService partServiceB = (EPartService) windowB.getContext().get(
				EPartService.class.getName());
		PartListener partListener = new PartListener();
		partServiceA.addPartListener(partListener);
		partServiceB.activate(partB);
		assertEquals(0, partListener.getVisible());
		assertEquals(0, partListener.getVisibleParts().size());
		assertTrue(partListener.isValid());
		partListener.clear();
		partServiceB.activate(partA);
		assertEquals(0, partListener.getVisible());
		assertEquals(0, partListener.getVisibleParts().size());
		assertTrue(partListener.isValid());
	}
	private void testSavePart(final Save returnValue, boolean confirm,
			boolean beforeDirty, boolean afterDirty, boolean success,
			boolean saveCalled, boolean throwException) {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		MPart saveablePart = BasicFactoryImpl.eINSTANCE.createPart();
		saveablePart.setDirty(beforeDirty);