Function createFiber

lib/assets/react-source/development/react.js:27357–27360

(tag, pendingProps, key, mode)

	var createFiber = function (tag, pendingProps, key, mode) {
	  // $FlowFixMe: the shapes are exact here but Flow doesn't like constructors
	  return new FiberNode(tag, pendingProps, key, mode);
	};

	function shouldConstruct(Component) {
	  var prototype = Component.prototype;