Bug 321755 EPS adds a part without considering its placeholder if no target container or part stacks could be found
The summary probably makes no sense. Will deliver a fix with a test in a bit.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
partService.activate(partA);
		MPart partB = partService.showPart("partId", partState);
		
		assertNotNull("The part should have been rendered", partB.getContext());
	}
	public void testShowPart_Bug307747_CREATE() {
		testShowPart_Bug307747(PartState.CREATE);
	}
	public void testShowPart_Bug307747_VISIBLE() {
		testShowPart_Bug307747(PartState.VISIBLE);
	}
	public void testShowPart_Bug307747_ACTIVATE() {
		testShowPart_Bug307747(PartState.ACTIVATE);
	}
	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();