Add backup element queue to CustomElementReactionStack

third_party/WebKit/Source/core/dom/custom/CEReactionsScope.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/dom/custom/CEReactionsScope.h"
 
 #include "core/dom/Document.h"
 #include "core/dom/Element.h"
 #include "core/dom/custom/CustomElementReactionStack.h"
 #include "core/frame/FrameHost.h"
 
 namespace blink {
 
 CEReactionsScope* CEReactionsScope::s_topOfStack = nullptr;
 
-void CEReactionsScope::enqueue(
+void CEReactionsScope::enqueueToCurrentQueue(
     Element* element,
     CustomElementReaction* reaction)
 {
     if (!m_frameHost.get()) {
         m_frameHost = element->document().frameHost();
         m_frameHost->customElementReactionStack().push();
+    } else {
+        DCHECK_EQ(m_frameHost, element->document().frameHost());
     }
-    m_frameHost->customElementReactionStack().enqueue(element, reaction);
+    m_frameHost->customElementReactionStack().enqueueToCurrentQueue(
+        element, reaction);
 }
 
 void CEReactionsScope::invokeReactions()
 {
     m_frameHost->customElementReactionStack().popInvokingReactions();
 }
 
 } // namespace blink