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

Source/core/accessibility/AccessibilityMenuList.cpp

Index: Source/core/accessibility/AccessibilityMenuList.cpp
diff --git a/Source/core/accessibility/AccessibilityMenuList.cpp b/Source/core/accessibility/AccessibilityMenuList.cpp
index b84ab0a807e2f6a9a1ce21008d18dff1ac8c13d6..46dd227a98eb3cfff580b669c6f38dbc3f9772a3 100644
--- a/Source/core/accessibility/AccessibilityMenuList.cpp
+++ b/Source/core/accessibility/AccessibilityMenuList.cpp
@@ -56,7 +56,7 @@ void AccessibilityMenuList::addChildren()
 {
     m_haveChildren = true;
 
-    AXObjectCache* cache = m_renderer->document()->axObjectCache();
+    AXObjectCache* cache = m_renderer->document().axObjectCache();
 
     AccessibilityObject* list = cache->getOrCreate(MenuListPopupRole);
     if (!list)
@@ -97,7 +97,7 @@ bool AccessibilityMenuList::canSetFocusAttribute() const
 
 void AccessibilityMenuList::didUpdateActiveOption(int optionIndex)
 {
-    RefPtr<Document> document = m_renderer->document();
+    RefPtr<Document> document = &m_renderer->document();
     AXObjectCache* cache = document->axObjectCache();
 
     const AccessibilityChildrenVector& childObjects = children();