From 9d4cc7cce4047c265bce231069fb6ef49d26d654 Mon Sep 17 00:00:00 2001
From: Brian Vaughn <bvaughn@fb.com>
Date: Fri, 9 Jun 2017 13:14:58 -0700
Subject: [PATCH] Check before overriding global.performance

Reviewed By: gaearon

Differential Revision: D5218876

fbshipit-source-id: 7fbe9ca020774a0c53d8cbb64996680112828709
---
 Libraries/Core/InitializeCore.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Libraries/Core/InitializeCore.js b/Libraries/Core/InitializeCore.js
index 6e00fe10696..4b6cac529fe 100644
--- a/Libraries/Core/InitializeCore.js
+++ b/Libraries/Core/InitializeCore.js
@@ -100,7 +100,9 @@ if (!global.process.env.NODE_ENV) {
 const Systrace = require('Systrace');
 Systrace.setEnabled(global.__RCTProfileIsProfiling || false);
 if (__DEV__) {
-  global.performance = Systrace.getUserTimingPolyfill();
+  if (global.performance === undefined) {
+    global.performance = Systrace.getUserTimingPolyfill();
+  }
 }
 
 // Set up console