From d31bdf2cf8f74a398efede27cc850e05a6655f30 Mon Sep 17 00:00:00 2001
From: Charlie Croom <ccroom@twitter.com>
Date: Tue, 9 Oct 2018 16:51:29 -0700
Subject: [PATCH] [fix] ResizeObserve only on elements using 'onLayout' prop

Only observe nodes when the 'onLayout' prop is specified on the
element. Fixes performance regression for browsers that rely on
MutationObserver-based shim for ResizeObserver.

Fix #1128
Close #1129
---
 .../react-native-web/src/modules/applyLayout/index.js     | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/packages/react-native-web/src/modules/applyLayout/index.js b/packages/react-native-web/src/modules/applyLayout/index.js
index 4fd58ae3e..d6e8a1a48 100644
--- a/packages/react-native-web/src/modules/applyLayout/index.js
+++ b/packages/react-native-web/src/modules/applyLayout/index.js
@@ -97,7 +97,9 @@ const applyLayout = Component => {
     function componentDidMount() {
       this._layoutState = emptyObject;
       this._isMounted = true;
-      observe(this);
+      if (this.props.onLayout) {
+        observe(this);
+      }
     }
   );
 
@@ -116,7 +118,9 @@ const applyLayout = Component => {
     componentWillUnmount,
     function componentWillUnmount() {
       this._isMounted = false;
-      unobserve(this);
+      if (this.props.onLayout) {
+        unobserve(this);
+      }
     }
   );