Added ReactFabric shim (#12216)

scripts/rollup/shims/react-native/ReactFabric.js

@@ -0,0 +1,23 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @providesModule ReactFabric
+ * @flow
+ */
+'use strict';
+
+// TODO @sema: Adjust types
+import type {ReactNativeType} from 'ReactNativeTypes';
+
+let ReactFabric;
+
+if (__DEV__) {
+  ReactFabric = require('ReactFabric-dev');
+} else {
+  ReactFabric = require('ReactFabric-prod');
+}
+
+module.exports = (ReactFabric: ReactNativeType);