Marker CSS class name for all container elements of a single formControl rendering. The ControlRenderer implementation must apply this to all container elements until the base level, where the label and the control itself are exposed.
Should be applied by ControlRenderer implementations to the label element, if its control is "one single line" like an inputField or a selectField.
Should be applied by ControlRenderer implementations to the legend element if its control renders a group of options like a checkboxGroup.