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
assertEquals(2, parts.size());
		assertTrue(parts.containsAll(partStack.getChildren()));
	}
	public void testGetParts_TwoWindows() {
		MApplication application = createApplication(new String[] { "partId",
				"partId2" }, new String[] { "partIA", "partIdB", "partIdC" });
		MWindow windowA = application.getChildren().get(0);
		MWindow windowB = application.getChildren().get(1);
		getEngine().createGui(windowA);
		getEngine().createGui(windowB);
		EPartService partServiceA = (EPartService) windowA.getContext().get(
				EPartService.class.getName());
		EPartService partServiceB = (EPartService) windowB.getContext().get(
				EPartService.class.getName());
		MPartStack partStackA = (MPartStack) windowA.getChildren().get(0);
		MPartStack partStackB = (MPartStack) windowB.getChildren().get(0);
		Collection<MPart> partsA = partServiceA.getParts();
		Collection<MPart> partsB = partServiceB.getParts();
		assertNotNull(partsA);
		assertEquals(2, partsA.size());
		assertTrue(partsA.containsAll(partStackA.getChildren()));
		assertNotNull(partsB);
		assertEquals(3, partsB.size());
		assertTrue(partsB.containsAll(partStackB.getChildren()));
		for (MPart partA : partsA) {
			assertFalse(partsB.contains(partA));
		}
	}
	public void testGetInputParts() {
		final String uri1 = "file:///a.txt";