Bug 318713 Duplicate toolbar items (navigate group)
SDK 4.0 - I20100701-1105. 1. start fresh workspace ==> navigate group appears twice which is quite confusing and wastes space.
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/TrimBarRenderer.java
return null;
		final MTrimBar trimModel = (MTrimBar) element;
		TrimmedPartLayout tpl = (TrimmedPartLayout) parentComp.getLayout();
		Composite result = null;
		switch (trimModel.getSide().getValue()) {
		case SideValue.TOP_VALUE:
			result = tpl.getTrimComposite(parentComp, SWT.TOP);
			break;
		case SideValue.BOTTOM_VALUE:
			result = tpl.getTrimComposite(parentComp, SWT.BOTTOM);
			break;
		case SideValue.LEFT_VALUE:
			result = tpl.getTrimComposite(parentComp, SWT.LEFT);
			break;
		case SideValue.RIGHT_VALUE:
			result = tpl.getTrimComposite(parentComp, SWT.RIGHT);
			break;
		default:
			return null;
		}
		result.addDisposeListener(new DisposeListener() {
			public void widgetDisposed(DisposeEvent e) {
				cleanUp(trimModel);
			}
		});
		return result;
	}
	@Override
	public void hideChild(MElementContainer<MUIElement> parentElement,
			MUIElement child) {