move the ReactNativeFeatureFlags outside of sync dir

Reviewed By: bvaughn

Differential Revision: D5627037

fbshipit-source-id: 0544b822ba03090a74695911b6951e91262478a0

Libraries/ReactNative/ReactNativeFeatureFlags.js

@@ -0,0 +1,46 @@
+/**
+ * Copyright 2013-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule ReactNativeFeatureFlags
+ * @flow
+ */
+
+'use strict';
+
+// =============================================================================
+// IMPORTANT:
+// When syncing React Renderer, make sure the feature flags are still compatible
+// =============================================================================
+
+var useFiber;
+
+var ReactNativeFeatureFlags = {
+  get useFiber(): boolean {
+    if (useFiber == null) {
+      useFiber = true;
+      if (__DEV__) {
+        require('Systrace').installReactHook(useFiber);
+      }
+    }
+    return useFiber;
+  },
+  set useFiber(enabled: boolean): void {
+    if (useFiber != null) {
+      throw new Error(
+        'Cannot set useFiber feature flag after it has been accessed. ' +
+        'Please override it before requiring React.',
+      );
+    }
+    useFiber = enabled;
+    if (__DEV__) {
+      require('Systrace').installReactHook(useFiber);
+    }
+  },
+};
+
+module.exports = ReactNativeFeatureFlags;