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
private void testHidePart_Bug327044(boolean force) {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		application.setSelectedElement(window);
		MPartStack stack = BasicFactoryImpl.eINSTANCE.createPartStack();
		window.getChildren().add(stack);
		window.setSelectedElement(stack);
		MPart part = BasicFactoryImpl.eINSTANCE.createPart();
		stack.getChildren().add(part);
		stack.setSelectedElement(part);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		window.getContext().get(EPartService.class).hidePart(part, force);
		assertNull(stack.getSelectedElement());
	}
	public void testHidePart_Bug327044_True() {
		testHidePart_Bug327044(true);
	}
	public void testHidePart_Bug327044_False() {
		testHidePart_Bug327044(false);
	}
	private void testHidePart_Bug327765(boolean force) {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		application.setSelectedElement(window);
		MPart part = BasicFactoryImpl.eINSTANCE.createPart();