[WIP] Custom element upgrades

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

 // 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 CustomElementDefinition_h
 #define CustomElementDefinition_h
 
 #include "core/CoreExport.h"
 #include "core/dom/custom/CustomElementDescriptor.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Noncopyable.h"
 
 namespace blink {
 
+class Element;
+
 class CORE_EXPORT CustomElementDefinition
     : public GarbageCollectedFinalized<CustomElementDefinition> {
     WTF_MAKE_NONCOPYABLE(CustomElementDefinition);
 public:
     CustomElementDefinition(const CustomElementDescriptor&);
     virtual ~CustomElementDefinition();
 
     const CustomElementDescriptor& descriptor() { return m_descriptor; }
 
-    DEFINE_INLINE_VIRTUAL_TRACE() { }
+    DECLARE_VIRTUAL_TRACE();
+
+    using ConstructionStack = HeapVector<Member<Element>, 1>;
+    ConstructionStack& constructionStack()
+    {
+        return m_constructionStack;
+    }
+
+    virtual bool upgrade(Element*) = 0;
 
 private:
     const CustomElementDescriptor m_descriptor;
+    ConstructionStack m_constructionStack;
 };
 
 } // namespace blink
 
 #endif // CustomElementDefinition_h