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

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 26 matching lines @@
 void TreeScopeAdopter::moveTreeToNewScope(Node& root) const
 {
     ASSERT(needsScopeChange());
 
     m_oldScope.guardRef();
 
     // 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.documentScope();
-    ASSERT(oldDocument);
-    Document* newDocument = m_newScope.documentScope();
+    Document& oldDocument = m_oldScope.documentScope();
+    Document& newDocument = m_newScope.documentScope();
     bool willMoveToNewDocument = oldDocument != newDocument;
     if (willMoveToNewDocument)
-        oldDocument->incDOMTreeVersion();
+        oldDocument.incDOMTreeVersion();
 
     for (Node* node = &root; node; node = NodeTraversal::next(*node, &root)) {
         updateTreeScope(*node);
 
         if (willMoveToNewDocument)
-            moveNodeToNewDocument(*node, *oldDocument, newDocument);
+            moveNodeToNewDocument(*node, oldDocument, newDocument);
         else if (node->hasRareData()) {
             NodeRareData* rareData = node->rareData();
             if (rareData->nodeLists())
                 rareData->nodeLists()->adoptTreeScope();
         }
 
         if (!node->isElementNode())
             continue;
 
         if (node->hasSyntheticAttrChildNodes()) {
             const Vector<RefPtr<Attr> >& attrs = toElement(node)->attrNodeList();
             for (unsigned i = 0; i < attrs.size(); ++i)
                 moveTreeToNewScope(*attrs[i]);
         }
 
         for (ShadowRoot* shadow = node->youngestShadowRoot(); shadow; shadow = shadow->olderShadowRoot()) {
             shadow->setParentTreeScope(&m_newScope);
             if (willMoveToNewDocument)
-                moveTreeToNewDocument(*shadow, *oldDocument, newDocument);
+                moveTreeToNewDocument(*shadow, oldDocument, newDocument);
         }
     }
 
     m_oldScope.guardDeref();
 }
 
-void TreeScopeAdopter::moveTreeToNewDocument(Node& root, Document& oldDocument, Document* newDocument) const
+void TreeScopeAdopter::moveTreeToNewDocument(Node& root, Document& oldDocument, Document& newDocument) const
 {
     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);
     m_newScope.guardRef();
     m_oldScope.guardDeref();
     node.setTreeScope(&m_newScope);
 }
 
-inline void TreeScopeAdopter::moveNodeToNewDocument(Node& node, Document& oldDocument, Document* newDocument) const
+inline void TreeScopeAdopter::moveNodeToNewDocument(Node& node, Document& oldDocument, Document& newDocument) const
 {
     ASSERT(!node.inDocument() || oldDocument != newDocument);
 
     if (node.hasRareData()) {
         NodeRareData* rareData = node.rareData();
         if (rareData->nodeLists())
-            rareData->nodeLists()->adoptDocument(&oldDocument, newDocument);
+            rareData->nodeLists()->adoptDocument(oldDocument, newDocument);
     }
 
-    oldDocument.moveNodeIteratorsToNewDocument(&node, newDocument);
+    oldDocument.moveNodeIteratorsToNewDocument(node, newDocument);
 
     if (node.isShadowRoot())
         toShadowRoot(node).setDocumentScope(newDocument);
 
 #ifndef NDEBUG
     didMoveToNewDocumentWasCalled = false;
     oldDocumentDidMoveToNewDocumentWasCalledWith = &oldDocument;
 #endif
 
     node.didMoveToNewDocument(oldDocument);
     ASSERT(didMoveToNewDocumentWasCalled);
 }
 
 }