Make Custom Element registration context creation explicit.

Source/core/dom/DocumentInit.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
@@ skipping 48 matching lines @@
     bool isSeamlessAllowedFor(Document* child) const;
     SandboxFlags sandboxFlags() const;
 
     Document* parent() const { return m_parent.get(); }
     Document* owner() const { return m_owner.get(); }
     KURL parentBaseURL() const;
     Frame* ownerFrame() const;
     Settings* settings() const;
 
     DocumentInit& withRegistrationContext(CustomElementRegistrationContext*);
-
+    DocumentInit& withNewRegistrationContext();
     PassRefPtr<CustomElementRegistrationContext> registrationContext(Document*) const;
     WeakPtr<Document> contextDocument() const;
 
     static DocumentInit fromContext(WeakPtr<Document> contextDocument, const KURL& = KURL());
 
 private:
     Frame* frameForSecurityContext() const;
 
     KURL m_url;
     Frame* m_frame;
     RefPtr<Document> m_parent;
     RefPtr<Document> m_owner;
     WeakPtr<Document> m_contextDocument;
     HTMLImport* m_import;
     RefPtr<CustomElementRegistrationContext> m_registrationContext;
+    bool m_createNewRegistrationContext;
 };
 
 } // namespace WebCore
 
 #endif // DocumentInit_h