Let unresolved custom element go through CustomElementCallbackQueue.

Source/core/dom/custom/CustomElementRegistrationContext.h

Index: Source/core/dom/custom/CustomElementRegistrationContext.h
diff --git a/Source/core/dom/custom/CustomElementRegistrationContext.h b/Source/core/dom/custom/CustomElementRegistrationContext.h
index 97dbc5fbfa75758737e331ebd010cc5fe256511d..cbd1b61dbd373bc8ee46cf95441b7f2d106cd786 100644
--- a/Source/core/dom/custom/CustomElementRegistrationContext.h
+++ b/Source/core/dom/custom/CustomElementRegistrationContext.h
@@ -60,6 +60,9 @@ public:
     static void setIsAttributeAndTypeExtension(Element*, const AtomicString& type);
     static void setTypeExtension(Element*, const AtomicString& type);
 
+    // Late resolution attempt from invocation object.
+    void resolvePoppedElement(Element*, const CustomElementDescriptor&);
+
 protected:
     CustomElementRegistrationContext() { }
 
@@ -67,9 +70,10 @@ protected:
     void didGiveTypeExtension(Element*, const AtomicString& type);
 
 private:
-    void resolve(Element*, const AtomicString& typeExtension);
+    void resolveNewElement(Element*, const AtomicString& typeExtension);
     void didResolveElement(CustomElementDefinition*, Element*);
     void didCreateUnresolvedElement(const CustomElementDescriptor&, Element*);
+    void didFailResolution(const CustomElementDescriptor&, Element*);
 
     CustomElementRegistry m_registry;