Bug 137442 [DataBinding] (C)ComboObservableValue should bind to selection index
3.2M6: I propose to extend (C)ComboObservableValue such that they could bind int.class values for pure selection changes of an otherwise immutable combo content. E.g. swtbinding allows such binding to an index holder and the class would attach as SelectionListener where it asks the combo for its selection index. Maybe the corresponding property should be assigned to SWTProperties.SELECTION_INDEX. Similar arguments could be given for corresponding extensions for SWT-List widgets.
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/swt/SWTObservables.java
}
	/**
	 * @param control
	 * @return an observable value tracking the font of the given control
	 */
	public static ISWTObservableValue observeFont(Control control) {
		return new ControlObservableValue(control, SWTProperties.FONT);
	}
	
	/**
	 * Returns an observable observing the editable attribute of
	 * the provided <code>control</code>. The supported types are:
	 * <ul>
	 * <li>org.eclipse.swt.widgets.Text</li>
	 * </ul>
	 * 
	 * @param control
	 * @return observable value
	 * @throws IllegalArgumentException
	 *             if <code>control</code> type is unsupported
	 */
	public static ISWTObservableValue observeEditable(Control control) {
		if (control instanceof Text) {
			return new TextEditableObservableValue((Text) control);
		}
		
		throw new IllegalArgumentException(
				"Widget [" + control.getClass().getName() + "] is not supported."); 
	}
	private static class DisplayRealm extends Realm {