Have Node::document() return a reference instead of a pointer

Source/core/page/DOMSelection.cpp

Index: Source/core/page/DOMSelection.cpp
diff --git a/Source/core/page/DOMSelection.cpp b/Source/core/page/DOMSelection.cpp
index 2bc803c05bb1612a3fe270c66354e2c65505ef97..b9a85af24cfe6f56e28b1b74f090f1bb6e1b0261 100644
--- a/Source/core/page/DOMSelection.cpp
+++ b/Source/core/page/DOMSelection.cpp
@@ -60,7 +60,7 @@ static Node* selectionShadowAncestor(Frame* frame)
 }
 
 DOMSelection::DOMSelection(const TreeScope* treeScope)
-    : DOMWindowProperty(treeScope->rootNode()->document()->frame())
+    : DOMWindowProperty(treeScope->rootNode()->document().frame())
     , m_treeScope(treeScope)
 {
     ScriptWrappable::init(this);
@@ -381,7 +381,7 @@ PassRefPtr<Range> DOMSelection::getRangeAt(int index, ExceptionState& es)
     if (Node* shadowAncestor = selectionShadowAncestor(m_frame)) {
         ContainerNode* container = shadowAncestor->parentNodeGuaranteedHostFree();
         int offset = shadowAncestor->nodeIndex();
-        return Range::create(shadowAncestor->document(), container, offset, container, offset);
+        return Range::create(&shadowAncestor->document(), container, offset, container, offset);
     }
 
     const VisibleSelection& selection = m_frame->selection()->selection();
@@ -463,7 +463,7 @@ bool DOMSelection::containsNode(const Node* n, bool allowPartial) const
 
     FrameSelection* selection = m_frame->selection();
 
-    if (!n || m_frame->document() != n->document() || selection->isNone())
+    if (!n || m_frame->document() != &n->document() || selection->isNone())
         return false;
 
     unsigned nodeIndex = n->nodeIndex();
@@ -545,7 +545,7 @@ bool DOMSelection::isValidForPosition(Node* node) const
     ASSERT(m_frame);
     if (!node)
         return true;
-    return node->document() == m_frame->document();
+    return &node->document() == m_frame->document();
 }
 
 } // namespace WebCore