Oilpan: cleanup based on review comments after removal of TreeShared.

Source/core/dom/Document.cpp

 /*
  * 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, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 2230 matching lines @@
     // or this setting of the frame to 0 could be made explicit in each of the
     // callers of Document::detach().
     m_frame = 0;
 
     if (m_mediaQueryMatcher)
         m_mediaQueryMatcher->documentDestroyed();
 
     lifecycleNotifier().notifyDocumentWasDetached();
     m_lifecycle.advanceTo(DocumentLifecycle::Stopped);
 #if ENABLE(OILPAN)
+    // FIXME: Oilpan: With Oilpan dispose should not be needed. At
+    // this point we still have dispose in order to clear out some
+    // RefPtrs that would otherwise cause leaks. However, when the
+    // Document is detached the document can still be alive, so we
+    // really shouldn't clear anything at this point. It should just
+    // die with the document when the document is no longer reachable.
     dispose();
 #endif
 }
 
 void Document::prepareForDestruction()
 {
     m_markers->prepareForDestruction();
     disconnectDescendantFrames();
 
     // The process of disconnecting descendant frames could have already detached us.
@@ skipping 3441 matching lines @@
     visitor->trace(m_visibilityObservers);
     visitor->trace(m_userActionElements);
     visitor->registerWeakMembers<Document, &Document::clearWeakMembers>(this);
     DocumentSupplementable::trace(visitor);
     TreeScope::trace(visitor);
     ContainerNode::trace(visitor);
     ExecutionContext::trace(visitor);
 }
 
 } // namespace WebCore