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

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

Index: third_party/WebKit/Source/core/dom/custom/CustomElementReactionQueue.cpp
diff --git a/third_party/WebKit/Source/core/dom/custom/CustomElementReactionQueue.cpp b/third_party/WebKit/Source/core/dom/custom/CustomElementReactionQueue.cpp
index 9f82b24c7c2d35e570ccd079026a31e5d5565303..f1341f29c60c6418304fe889987e2353cfa71c15 100644
--- a/third_party/WebKit/Source/core/dom/custom/CustomElementReactionQueue.cpp
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElementReactionQueue.cpp
@@ -32,6 +32,10 @@ void CustomElementReactionQueue::invokeReactions(Element* element) {
   // 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);
 }