Add forked copies of reconciler modules

packages/react-reconciler/src/ReactCapturedValue.new.js

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+import type {Fiber} from './ReactFiber.new';
+
+import {getStackByFiberInDevAndProd} from './ReactFiberComponentStack';
+
+export type CapturedValue<T> = {|
+  value: T,
+  source: Fiber | null,
+  stack: string | null,
+|};
+
+export function createCapturedValue<T>(
+  value: T,
+  source: Fiber,
+): CapturedValue<T> {
+  // If the value is an error, call this function immediately after it is thrown
+  // so the stack is accurate.
+  return {
+    value,
+    source,
+    stack: getStackByFiberInDevAndProd(source),
+  };
+}