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
private Shell shell;
	protected void setUp() {
		shell = new Shell();
		RealmTester.setDefault(SWTObservables.getRealm(shell.getDisplay()));
	}
	protected void tearDown() throws Exception {
		if (shell != null && !shell.isDisposed()) {
			shell.dispose();
		}
		RealmTester.setDefault(null);
	}
	public void testObserveForeground() throws Exception {
		ISWTObservableValue value = SWTObservables.observeForeground(shell);
		assertNotNull(value);
		assertEquals(Color.class, value.getValueType());
	}
	public void testObserveBackground() throws Exception {
		ISWTObservableValue value = SWTObservables.observeBackground(shell);
		assertNotNull(value);
		assertEquals(Color.class, value.getValueType());
	}
	public void testObserveFont() throws Exception {
		ISWTObservableValue value = SWTObservables.observeFont(shell);
		assertNotNull(value);
		assertEquals(Font.class, value.getValueType());
	}