From b58207e61fcb3fb0444860ba11b8a62aff7836c9 Mon Sep 17 00:00:00 2001
From: Kevin Gozali <fkg@fb.com>
Date: Mon, 14 Aug 2017 10:51:16 -0700
Subject: [PATCH] remove internal copy of ReactNativeFeatureFlags

Reviewed By: bvaughn, davidaurelio

Differential Revision: D5618991

fbshipit-source-id: 8b93bca186523585732c2177540189a1d83f9c90
---
 .../Renderer/shims/ReactNativeFeatureFlags.js | 28 +++++++++++++++----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/Libraries/Renderer/shims/ReactNativeFeatureFlags.js b/Libraries/Renderer/shims/ReactNativeFeatureFlags.js
index 17719817959..035f135e905 100644
--- a/Libraries/Renderer/shims/ReactNativeFeatureFlags.js
+++ b/Libraries/Renderer/shims/ReactNativeFeatureFlags.js
@@ -12,12 +12,30 @@
 
 'use strict';
 
+var useFiber;
+
 var ReactNativeFeatureFlags = {
-  useFiber: false,
+  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);
+    }
+  },
 };
 
-if (__DEV__) {
-  require('Systrace').installReactHook(false);
-}
-
 module.exports = ReactNativeFeatureFlags;