Oilpan: move DOMImplementation to the heap.

Source/core/dom/Document.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) 2011 Google Inc. All rights reserved.
  *
@@ skipping 1194 matching lines @@
     KURL m_baseURLOverride; // An alternative base URL that takes precedence over m_baseURL (but not m_baseElementURL).
     KURL m_baseElementURL; // The URL set by the <base> element.
     KURL m_cookieURL; // The URL to use for cookie access.
 
     AtomicString m_baseTarget;
 
     // Mime-type of the document in case it was cloned or created by XHR.
     AtomicString m_mimeType;
 
     RefPtrWillBeMember<DocumentType> m_docType;
-    OwnPtr<DOMImplementation> m_implementation;
+    OwnPtrWillBeMember<DOMImplementation> m_implementation;
 
     RefPtrWillBeMember<CSSStyleSheet> m_elemSheet;
 
     bool m_printing;
     bool m_paginatedForScreen;
 
     CompatibilityMode m_compatibilityMode;
     bool m_compatibilityModeLocked; // This is cheaper than making setCompatibilityMode virtual.
 
     bool m_hasAutofocused;
@@ skipping 217 matching lines @@
 inline bool Node::isDocumentNode() const
 {
     return this == document();
 }
 
 Node* eventTargetNodeForDocument(Document*);
 
 } // namespace WebCore
 
 #endif // Document_h