From dfebcb70a5c948db94d1cd580bbcaa0aaa702349 Mon Sep 17 00:00:00 2001
From: Alexey Lang <alexeylang@fb.com>
Date: Fri, 1 Dec 2017 02:37:06 -0800
Subject: [PATCH] Don't set global.performance to undefined if it was
 initialized already

Reviewed By: gaearon

Differential Revision: D6448731

fbshipit-source-id: 8c8c6ff393e452c863f54c83c2e4394fd535dfc5
---
 Libraries/Performance/Systrace.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Libraries/Performance/Systrace.js b/Libraries/Performance/Systrace.js
index d9a8908f9..6e09bc6cf 100644
--- a/Libraries/Performance/Systrace.js
+++ b/Libraries/Performance/Systrace.js
@@ -161,7 +161,9 @@ const Systrace = {
         }
         if (_canInstallReactHook) {
           if (_useFiber) {
-            global.performance = enabled ? userTimingPolyfill : undefined;
+            if (enabled && global.performance === undefined) {
+              global.performance = userTimingPolyfill;
+            }
           } else {
             const ReactDebugTool = require('ReactDebugTool');
             if (enabled) {