Bug 326177 EPartService's getActivePart() does not appear to work properly for an application with multiple windows
Based on the code in PartServiceCreationFunction, the EPartService implementation being returned when an application's context is queried seems to be a window-level EPartService implementation.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
public void testSavePart_NoHandler_TTF() {
		testSavePart_NoHandler(true, true, false);
	}
	public void testSavePart_NoHandler_TFT() {
		testSavePart_NoHandler(true, false, true);
	}
	public void testSavePart_NoHandler_TFF() {
		testSavePart_NoHandler(true, false, false);
	}
	public void testSavePart_NoHandler_FTT() {
		testSavePart_NoHandler(false, true, true);
	}
	public void testSavePart_NoHandler_FTF() {
		testSavePart_NoHandler(false, true, false);
	}
	public void testSavePart_NoHandler_FFT() {
		testSavePart_NoHandler(false, false, true);
	}
	public void testSavePart_NoHandler_FFF() {
		testSavePart_NoHandler(false, false, false);
	}
	private MPart createSaveablePart(
			MElementContainer<MWindowElement> container, boolean beforeDirty) {
		MPart saveablePart = BasicFactoryImpl.eINSTANCE.createPart();
		saveablePart.setDirty(beforeDirty);
		saveablePart
				.setContributionURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.application.ClientEditor");
		container.getChildren().add(saveablePart);
		return saveablePart;
	}