testEnterDocumentForNonFocusableControl() {
    control.setSupportedState(Component.State.FOCUSED, false);
    control.render(sandbox);
    assertTrue('Control must be in the document', control.isInDocument());
    assertEquals(
        'Control must have 5 mouse event listeners', 5,
        getListenerCount(control));
    assertUndefined(
        'Control must not have a key event handler', control.keyHandler_);
  }
Tests {@link Control#enterDocument} for a control that isn't
focusable.
@suppress {visibility} suppression added to enable type checking