Add a queue for custom element reactions.

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

Index: third_party/WebKit/Source/core/dom/custom/CustomElementReactionQueue.h
diff --git a/third_party/WebKit/Source/core/dom/custom/CustomElementReactionQueue.h b/third_party/WebKit/Source/core/dom/custom/CustomElementReactionQueue.h
new file mode 100644
index 0000000000000000000000000000000000000000..280d8f862889d90778b493d88c4c7f5942149e41
--- /dev/null
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElementReactionQueue.h
@@ -0,0 +1,36 @@
+// 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.
+
+#ifndef CustomElementReactionQueue_h
+#define CustomElementReactionQueue_h
+
+#include "core/CoreExport.h"
+#include "platform/heap/Handle.h"
+#include "wtf/Noncopyable.h"
+
+namespace blink {
+
+class CustomElementReaction;
+class Element;
+
+class CORE_EXPORT CustomElementReactionQueue final
+    : public GarbageCollectedFinalized<CustomElementReactionQueue> {
+    WTF_MAKE_NONCOPYABLE(CustomElementReactionQueue);

[yosin_UTC9, 2016/06/01 02:14:01]

Better to use DISALLOW_COPY_AND_ASSIGN()?

+public:
+    CustomElementReactionQueue();
+    ~CustomElementReactionQueue();
+
+    DECLARE_TRACE();
+
+    void add(CustomElementReaction*);
+    void invokeReactions(Element*);
+
+private:
+    HeapVector<Member<CustomElementReaction>> m_reactions;
+    size_t m_index;
+};
+
+} // namespace blink
+
+#endif // CustomElementReactionQueue_h