* adapter is providing content
* @param proposalProvider the {@link XmlBackedContentProposalProvider} used
* to obtain content proposals for this control, or null if no content
*/
public ComboAttributeProposalAdapter(ComboAttribute attrControl, XmlBackedContentProposalProvider proposalProvider) {
super(attrControl.getComboControl(), new ComboContentAdapter(), proposalProvider, null);
comboAttr = attrControl;
}