[WIP] Custom element upgrades

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

Index: third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.h
diff --git a/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.h b/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.h
index e410349ac24f66484daacbb7c199e68be1822b60..717b895af2f5b9910503c5530c9a467fc6c2feb9 100644
--- a/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.h
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.h
@@ -12,6 +12,8 @@
 
 namespace blink {
 
+class Element;
+
 class CORE_EXPORT CustomElementDefinition
     : public GarbageCollectedFinalized<CustomElementDefinition> {
     WTF_MAKE_NONCOPYABLE(CustomElementDefinition);
@@ -21,10 +23,19 @@ public:
 
     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