Bug 207844 [DataBinding] Support SWTObservables.observeText for Shells.
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 {