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

Source/core/svg/SVGStyleElement.cpp

Index: Source/core/svg/SVGStyleElement.cpp
diff --git a/Source/core/svg/SVGStyleElement.cpp b/Source/core/svg/SVGStyleElement.cpp
index 1ae01497303c65ad195d34f76b9b4bcbf72175fc..acbdab78c1f856783ac05a3a1ba6ca6925267c90 100644
--- a/Source/core/svg/SVGStyleElement.cpp
+++ b/Source/core/svg/SVGStyleElement.cpp
@@ -40,7 +40,7 @@ inline SVGStyleElement::SVGStyleElement(const QualifiedName& tagName, Document*
 
 SVGStyleElement::~SVGStyleElement()
 {
-    StyleElement::clearDocumentData(document(), this);
+    StyleElement::clearDocumentData(&document(), this);
 }
 
 PassRefPtr<SVGStyleElement> SVGStyleElement::create(const QualifiedName& tagName, Document* document, bool createdByParser)
@@ -136,14 +136,14 @@ Node::InsertionNotificationRequest SVGStyleElement::insertedInto(ContainerNode*
 
 void SVGStyleElement::didNotifySubtreeInsertions(ContainerNode* insertionPoint)
 {
-    StyleElement::processStyleSheet(document(), this);
+    StyleElement::processStyleSheet(&document(), this);
 }
 
 void SVGStyleElement::removedFrom(ContainerNode* rootParent)
 {
     SVGElement::removedFrom(rootParent);
     if (rootParent->inDocument())
-        StyleElement::removedFromDocument(document(), this);
+        StyleElement::removedFromDocument(&document(), this);
 }
 
 void SVGStyleElement::childrenChanged(bool changedByParser, Node* beforeChange, Node* afterChange, int childCountDelta)