From beb8e5067e64b90f315a28b1031a95bf9f1c8146 Mon Sep 17 00:00:00 2001
From: William Chou <willchou@google.com>
Date: Thu, 16 Aug 2018 13:41:50 -0400
Subject: [PATCH] Avoid calling Object.assign before polyfill is installed.
 (#17544)

---
 src/polyfills.js | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/polyfills.js b/src/polyfills.js
index 7b574c8b929e..430e38befc00 100644
--- a/src/polyfills.js
+++ b/src/polyfills.js
@@ -28,14 +28,15 @@ import {installCustomElements as installRegisterElement} from
   'document-register-element/build/document-register-element.patched';
 import {isExperimentOn} from './experiments';
 
-if (isExperimentOn(self, 'custom-elements-v1') || getMode().test) {
-  installCustomElements(self, class {});
-} else {
-  installRegisterElement(self, 'auto');
-}
 installDOMTokenListToggle(self);
 installMathSign(self);
 installObjectAssign(self);
 installPromise(self);
 installDocContains(self);
 installArrayIncludes(self);
+// isExperimentOn() must be called after Object.assign polyfill is installed.
+if (isExperimentOn(self, 'custom-elements-v1') || getMode().test) {
+  installCustomElements(self, class {});
+} else {
+  installRegisterElement(self, 'auto');
+}