Custom elements should have class side inheritance.

sky/engine/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 180 matching lines @@
     else
         v8Type = v8::Null(isolate);
 
     m_constructor->SetName(v8Type->IsNull() ? v8TagName : v8Type.As<v8::String>());
 
     V8HiddenValue::setHiddenValue(isolate, m_constructor, V8HiddenValue::customElementDocument(isolate), toV8(document, m_scriptState->context()->Global(), isolate));
     V8HiddenValue::setHiddenValue(isolate, m_constructor, V8HiddenValue::customElementTagName(isolate), v8TagName);
     V8HiddenValue::setHiddenValue(isolate, m_constructor, V8HiddenValue::customElementType(isolate), v8Type);
 
     v8::Handle<v8::String> prototypeKey = v8String(isolate, "prototype");
+    v8::Handle<v8::String> constructorKey = v8String(isolate, "constructor");
+
     ASSERT(m_constructor->HasOwnProperty(prototypeKey));
     // This sets the property *value*; calling Set is safe because
     // "prototype" is a non-configurable data property so there can be
     // no side effects.
     m_constructor->Set(prototypeKey, m_prototype);
     // This *configures* the property. ForceSet of a function's
     // "prototype" does not affect the value, but can reconfigure the
     // property.
     m_constructor->ForceSet(prototypeKey, m_prototype, v8::PropertyAttribute(v8::ReadOnly | v8::DontEnum | v8::DontDelete));
+    // The generated constructor should inherit from your constructor.
+    m_constructor->SetPrototype(m_prototype->Get(constructorKey));
 
     V8HiddenValue::setHiddenValue(isolate, m_prototype, V8HiddenValue::customElementIsInterfacePrototypeObject(isolate), v8::True(isolate));
-    m_prototype->ForceSet(v8String(isolate, "constructor"), m_constructor, v8::DontEnum);
+    m_prototype->ForceSet(constructorKey, m_constructor, v8::DontEnum);
 
     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()) {
         CustomElementException::throwException(CustomElementException::PrototypeInUse, type, exceptionState);
         return false;
     }
@@ skipping 55 matching lines @@
 
     ExceptionState exceptionState(ExceptionState::ConstructionContext, "CustomElement", info.Holder(), info.GetIsolate());
     CustomElementProcessingStack::CallbackDeliveryScope deliveryScope;
     RefPtr<Element> element = document->createElement(tagName, maybeType->IsNull() ? nullAtom : type, exceptionState);
     if (exceptionState.throwIfNeeded())
         return;
     v8SetReturnValueFast(info, element.release(), document);
 }
 
 } // namespace blink