Bug 316298 [Compatibility] Support o.e.ui.menus visibleWhen
We need support in MCoreExpression for entire expressions created by the WorkbenchMenuService. They don't often use ReferenceExpressions to core expression definitions. PW
bundles/org.eclipse.e4.ui.workbench.swt/src/org/eclipse/e4/ui/workbench/swt/modeling/MenuServiceFilter.java
private void handleContextMenu(final Event event, final Menu menu,
			final MPopupMenu menuModel) {
		switch (event.type) {
		case SWT.Show:
			if (DEBUG) {
				trace("handleContextMenu.Show", menu, menuModel);
			}
			cleanUp(menu);
			showPopup(event, menu, menuModel);
			break;
		case SWT.Hide:
			if (DEBUG) {
				trace("handleContextMenu.Hide", menu, menuModel);
			}
			
			break;
		case SWT.Dispose:
			if (DEBUG) {
				trace("handleContextMenu.Dispose", menu, menuModel);
			}
			cleanUp(menu);
			break;
		}
	}
	private void showPopup(final Event event, final Menu menu,
			final MPopupMenu menuModel) {
		final IEclipseContext popupContext = menuModel.getContext();
		final IEclipseContext parentContext = popupContext.getParent();
		final IEclipseContext originalChild = (IEclipseContext) parentContext
				.getLocal(IContextConstants.ACTIVE_CHILD);