blurTextInput(textFieldNode: ?Object) {
    if (textFieldNode !== null) {
      this._currentlyFocusedNode = null;
      if (document.activeElement === textFieldNode) {
        UIManager.blur(textFieldNode);
      }
    }
  }
@param {Object} textFieldNode id of the text field to focus
Unfocuses the specified text field
noop if it wasn't focused