focusTextInput(textFieldNode: ?Object) {
    if (textFieldNode !== null) {
      this._currentlyFocusedNode = textFieldNode;
      if (document.activeElement !== textFieldNode) {
        UIManager.focus(textFieldNode);
      }
    }
  }
@param {Object} TextInputID id of the text field to focus
Focuses the specified text field
noop if the text field was already focused