[Reland] Implement Custom Element's class side inheritance

Source/bindings/core/v8/CustomElementConstructorBuilder.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 181 matching lines @@
     // "prototype" is a non-configurable data property so there can be
     // no side effects.
     if (!v8CallBoolean(m_constructor->Set(context, prototypeKey, m_prototype)))
         return false;
     // This *configures* the property. ForceSet of a function's
     // "prototype" does not affect the value, but can reconfigure the
     // property.
     if (!v8CallBoolean(m_constructor->ForceSet(context, prototypeKey, m_prototype, v8::PropertyAttribute(v8::ReadOnly | v8::DontEnum | v8::DontDelete))))
         return false;
 
+    v8::Local<v8::String> constructorKey = v8String(isolate, "constructor");
+    v8::Local<v8::Value> constructorPrototype;
+    if (!m_prototype->Get(context, constructorKey).ToLocal(&constructorPrototype))
+        return false;
+
+    if (!v8CallBoolean(m_constructor->SetPrototype(context, constructorPrototype)))
+        return false;
+
     V8HiddenValue::setHiddenValue(isolate, m_prototype, V8HiddenValue::customElementIsInterfacePrototypeObject(isolate), v8::True(isolate));
     if (!v8CallBoolean(m_prototype->ForceSet(context, v8String(isolate, "constructor"), m_constructor, v8::DontEnum)))
         return false;
 
     return true;
 }
 
 bool CustomElementConstructorBuilder::prototypeIsValid(const AtomicString& type, ExceptionState& exceptionState) const
 {
     if (m_prototype->InternalFieldCount() || !V8HiddenValue::getHiddenValue(m_scriptState->isolate(), m_prototype, V8HiddenValue::customElementIsInterfacePrototypeObject(m_scriptState->isolate())).IsEmpty()) {
@@ skipping 60 matching lines @@
 
     ExceptionState exceptionState(ExceptionState::ConstructionContext, "CustomElement", info.Holder(), info.GetIsolate());
     CustomElementProcessingStack::CallbackDeliveryScope deliveryScope;
     RefPtrWillBeRawPtr<Element> element = document->createElementNS(namespaceURI, tagName, maybeType->IsNull() ? nullAtom : type, exceptionState);
     if (exceptionState.throwIfNeeded())
         return;
     v8SetReturnValueFast(info, element.release(), document);
 }
 
 } // namespace blink