Clear the custom element's reaction queue if upgrade fails.

third_party/WebKit/Source/core/dom/custom/CustomElementReactionQueue.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/CustomElementReactionQueue.h"
 
 #include "core/dom/custom/CustomElementReaction.h"
 
 namespace blink {
 
@@ skipping 14 matching lines @@
 void CustomElementReactionQueue::invokeReactions(Element* element) {
   while (m_index < m_reactions.size()) {
     CustomElementReaction* reaction = m_reactions[m_index];
     m_reactions[m_index++] = nullptr;
     reaction->invoke(element);
   }
   // Unlike V0CustomElementsCallbackQueue, reactions are always
   // inserted by steps which bump the global element queue. This
   // means we do not need queue "owner" guards.
   // https://html.spec.whatwg.org/multipage/scripting.html#custom-element-reactions
+  clear();
+}
+
+void CustomElementReactionQueue::clear() {
   m_index = 0;
   m_reactions.resize(0);
 }
 
 }  // namespace blink