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
partService.switchPerspective(perspectiveB);
		partService.switchPerspective(perspectiveA);
		ClientEditor editorA = (ClientEditor) partA.getObject();
		ClientEditor editorB = (ClientEditor) partB.getObject();
		editorA.focusCalled = false;
		editorB.focusCalled = false;
		partService.switchPerspective(perspectiveB);
		assertFalse(editorA.focusCalled);
		assertTrue(editorB.focusCalled);
		editorB.focusCalled = false;
		partService.switchPerspective(perspectiveA);
		assertTrue(editorA.focusCalled);
		assertFalse(editorB.focusCalled);
	}
	private MApplication createApplication(String partId) {
		return createApplication(new String[] { partId });
	}
	private MApplication createApplication(String... partIds) {
		return createApplication(new String[][] { partIds });
	}
	private MApplication createApplication(String[]... partIds) {
		return createApplication(partIds.length, partIds);
	}
	private MApplication createApplication(int windows, String[][] partIds) {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		for (int i = 0; i < windows; i++) {
			MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
			application.getChildren().add(window);
			MPartStack partStack = BasicFactoryImpl.eINSTANCE.createPartStack();