Bug 279452 [Compatibility] Parameterized command mechanism support
Parameterized commands like showView need to be able to access their parameters (like the view ID) PW
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/workbench/HandlerTest.java
EHandlerService service = (EHandlerService) appContext
				.get(EHandlerService.class.getName());
		TestHandler handler = new TestHandler(true, HELP_COMMAND_ID);
		service.activateHandler(HELP_COMMAND_ID, handler);
		IEclipseContext window = createContext(appContext, "windowContext");
		appContext.set(IServiceConstants.ACTIVE_CHILD, window);
		EHandlerService windowService = (EHandlerService) window
				.get(EHandlerService.class.getName());
		String windowRC = HELP_COMMAND_ID + ".window";
		TestHandler windowHandler = new TestHandler(false, windowRC);
		windowService.activateHandler(HELP_COMMAND_ID, windowHandler);
		assertNull(service.executeHandler(HELP_COMMAND_ID));
		assertFalse(windowHandler.ran);
		assertFalse(handler.ran);
		windowHandler.canRun = true;
		assertEquals(windowRC, service.executeHandler(HELP_COMMAND_ID));
		assertTrue(windowHandler.ran);
		assertFalse(handler.ran);
	}
	public void testCanExecute() throws Exception {
		IEclipseContext appContext = createGlobalContext();
		defineCommands(appContext);
		EHandlerService service = (EHandlerService) appContext
				.get(EHandlerService.class.getName());
		TestHandler handler = new TestHandler(true, HELP_COMMAND_ID);
		service.activateHandler(HELP_COMMAND_ID, handler);
		IEclipseContext window = createContext(appContext, "windowContext");
		appContext.set(IServiceConstants.ACTIVE_CHILD, window);
		EHandlerService windowService = (EHandlerService) window
				.get(EHandlerService.class.getName());