Oilpan: Remove guardRef and guardDeref from TreeScope.

Source/core/dom/TreeScopeAdopter.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 20 matching lines @@
 #include "core/dom/NodeTraversal.h"
 #include "core/dom/shadow/ElementShadow.h"
 #include "core/dom/shadow/ShadowRoot.h"
 
 namespace WebCore {
 
 void TreeScopeAdopter::moveTreeToNewScope(Node& root) const
 {
     ASSERT(needsScopeChange());
 
+#if !ENABLE(OILPAN)
     m_oldScope.guardRef();
+#endif
 
     // If an element is moved from a document and then eventually back again the collection cache for
     // that element may contain stale data as changes made to it will have updated the DOMTreeVersion
     // of the document it was moved to. By increasing the DOMTreeVersion of the donating document here
     // we ensure that the collection cache will be invalidated as needed when the element is moved back.
     Document& oldDocument = m_oldScope.document();
     Document& newDocument = m_newScope.document();
     bool willMoveToNewDocument = oldDocument != newDocument;
     if (willMoveToNewDocument)
         oldDocument.incDOMTreeVersion();
@@ skipping 18 matching lines @@
                 moveTreeToNewScope(*attrs[i]);
         }
 
         for (ShadowRoot* shadow = node->youngestShadowRoot(); shadow; shadow = shadow->olderShadowRoot()) {
             shadow->setParentTreeScope(m_newScope);
             if (willMoveToNewDocument)
                 moveTreeToNewDocument(*shadow, oldDocument, newDocument);
         }
     }
 
+#if !ENABLE(OILPAN)
     m_oldScope.guardDeref();

[haraken, 2014/04/25 05:21:42]

Who keeps the old scope alive while we're moving the tree from the old scope to
the new scope? My question is whether it is safe to trigger GC while moving the
tree.

[Mads Ager (chromium), 2014/04/25 10:58:25]

TreeScopeAdopter is STACK_ALLOCATED, so the pointers are on the stack. Marked
TreeScopeAdopter as STACK_ALLOCATED.

+#endif
 }
 
 void TreeScopeAdopter::moveTreeToNewDocument(Node& root, Document& oldDocument, Document& newDocument) const
 {
     ASSERT(oldDocument != newDocument);
     for (Node* node = &root; node; node = NodeTraversal::next(*node, &root)) {
         moveNodeToNewDocument(*node, oldDocument, newDocument);
         for (ShadowRoot* shadow = node->youngestShadowRoot(); shadow; shadow = shadow->olderShadowRoot())
             moveTreeToNewDocument(*shadow, oldDocument, newDocument);
     }
 }
 
 #ifndef NDEBUG
 static bool didMoveToNewDocumentWasCalled = false;
 static Document* oldDocumentDidMoveToNewDocumentWasCalledWith = 0;
 
 void TreeScopeAdopter::ensureDidMoveToNewDocumentWasCalled(Document& oldDocument)
 {
     ASSERT(!didMoveToNewDocumentWasCalled);
     ASSERT_UNUSED(oldDocument, oldDocument == oldDocumentDidMoveToNewDocumentWasCalledWith);
     didMoveToNewDocumentWasCalled = true;
 }
 #endif
 
 inline void TreeScopeAdopter::updateTreeScope(Node& node) const
 {
     ASSERT(!node.isTreeScope());
     ASSERT(node.treeScope() == m_oldScope);
+#if !ENABLE(OILPAN)
     m_newScope.guardRef();
     m_oldScope.guardDeref();
+#endif
     node.setTreeScope(&m_newScope);
 }
 
 inline void TreeScopeAdopter::moveNodeToNewDocument(Node& node, Document& oldDocument, Document& newDocument) const
 {
     ASSERT(oldDocument != newDocument);
 
     if (node.hasRareData()) {
         NodeRareData* rareData = node.rareData();
         if (rareData->nodeLists())
             rareData->nodeLists()->adoptDocument(oldDocument, newDocument);
     }
 
     oldDocument.moveNodeIteratorsToNewDocument(node, newDocument);
 
     if (node.isShadowRoot())
         toShadowRoot(node).setDocument(newDocument);
 
 #ifndef NDEBUG
     didMoveToNewDocumentWasCalled = false;
     oldDocumentDidMoveToNewDocumentWasCalledWith = &oldDocument;
 #endif
 
     node.didMoveToNewDocument(oldDocument);
     ASSERT(didMoveToNewDocumentWasCalled);
 }
 
 }