Make TreeScope::documentScope() return a reference and ensure m_documentScope is never NULL

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 529 matching lines @@
     // We must call clearRareData() here since a Document class inherits TreeScope
     // as well as Node. See a comment on TreeScope.h for the reason.
     if (hasRareData())
         clearRareData();
 
     ASSERT(!m_listsInvalidatedAtDocument.size());
 
     for (unsigned i = 0; i < WTF_ARRAY_LENGTH(m_nodeListCounts); i++)
         ASSERT(!m_nodeListCounts[i]);
 
-    clearDocumentScope();
     setClient(0);
 
     InspectorCounters::decrementCounter(InspectorCounters::DocumentCounter);
 }
 
 void Document::dispose()
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun);
     // We must make sure not to be retaining any of our children through
     // these extra pointers or we will create a reference cycle.
@@ skipping 2931 matching lines @@
     m_nodeIterators.add(ni);
 }
 
 void Document::detachNodeIterator(NodeIterator* ni)
 {
     // The node iterator can be detached without having been attached if its root node didn't have a document
     // when the iterator was created, but has it now.
     m_nodeIterators.remove(ni);
 }
 
-void Document::moveNodeIteratorsToNewDocument(Node* node, Document* newDocument)
+void Document::moveNodeIteratorsToNewDocument(Node& node, Document& newDocument)
 {
     HashSet<NodeIterator*> nodeIteratorsList = m_nodeIterators;
     HashSet<NodeIterator*>::const_iterator nodeIteratorsEnd = nodeIteratorsList.end();
     for (HashSet<NodeIterator*>::const_iterator it = nodeIteratorsList.begin(); it != nodeIteratorsEnd; ++it) {
         if ((*it)->root() == node) {
             detachNodeIterator(*it);
-            newDocument->attachNodeIterator(*it);
+            newDocument.attachNodeIterator(*it);
         }
     }
 }
 
 void Document::updateRangesAfterChildrenChanged(ContainerNode* container)
 {
     if (!m_ranges.isEmpty()) {
         HashSet<Range*>::const_iterator end = m_ranges.end();
         for (HashSet<Range*>::const_iterator it = m_ranges.begin(); it != end; ++it)
             (*it)->nodeChildrenChanged(container);
@@ skipping 1745 matching lines @@
 }
 
 FastTextAutosizer* Document::fastTextAutosizer()
 {
     if (!m_fastTextAutosizer && RuntimeEnabledFeatures::fastTextAutosizingEnabled())
         m_fastTextAutosizer = FastTextAutosizer::create(this);
     return m_fastTextAutosizer.get();
 }
 
 } // namespace WebCore