Bug 176882 [DataBinding] Create SWTObservables.observeEditable(...)
We need to provide an observable for the editable property of Text.
tests/org.eclipse.jface.tests.databinding/src/org/eclipse/jface/tests/databinding/swt/SWTObservablesTest.java
public void testObserveSelectionOfList() throws Exception {
		List list = new List(shell, SWT.NONE);
		ISWTObservableValue value = SWTObservables.observeSelection(list);
		assertNotNull(value);
		assertTrue(value instanceof ListObservableValue);
	}
	
	public void testObserveSelectionOfScale() throws Exception {
		Scale scale = new Scale(shell, SWT.NONE);
		ISWTObservableValue value = SWTObservables.observeSelection(scale);
		assertNotNull(value);
		assertTrue(value instanceof ScaleObservableValue);
		
		ScaleObservableValue scaleObservable = (ScaleObservableValue) value;
		assertEquals(SWTProperties.SELECTION, scaleObservable.getAttribute());
	}
	public void testObserveSelectionOfUnsupportedControl() throws Exception {
		try {
			Text text = new Text(shell, SWT.NONE);
			SWTObservables.observeSelection(text);
			fail("Exception should have been thrown");
		} catch (IllegalArgumentException e) {
		}
	}
	public void testObserveTextOfText() throws Exception {
		Text text = new Text(shell, SWT.NONE);
		assertFalse(text.isListening(SWT.FocusOut));
		ISWTObservableValue value = SWTObservables.observeText(text,
				SWT.FocusOut);
		assertNotNull(value);