Don't set global.performance to undefined if it was initialized already

Reviewed By: gaearon Differential Revision: D6448731 fbshipit-source-id: 8c8c6ff393e452c863f54c83c2e4394fd535dfc5
facebook · Dec 1, 2017 · dfebcb7 · dfebcb7
1 parent 4fdaf2d
commit dfebcb7
Showing 1 changed file with 3 additions and 1 deletion.
diff --git 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) {