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

Source/core/css/resolver/ElementResolveContext.cpp

Index: Source/core/css/resolver/ElementResolveContext.cpp
diff --git a/Source/core/css/resolver/ElementResolveContext.cpp b/Source/core/css/resolver/ElementResolveContext.cpp
index b9973b3b91c8c86c82c877fe92be6000307ca221..f093d798dd2e4746db5c4fc9255caa190fa32051 100644
--- a/Source/core/css/resolver/ElementResolveContext.cpp
+++ b/Source/core/css/resolver/ElementResolveContext.cpp
@@ -31,7 +31,7 @@ namespace WebCore {
 
 ElementResolveContext::ElementResolveContext(Element* element)
     : m_element(element)
-    , m_elementLinkState(element ? element->document()->visitedLinkState()->determineLinkState(element) : NotInsideLink)
+    , m_elementLinkState(element ? element->document().visitedLinkState()->determineLinkState(element) : NotInsideLink)
     , m_distributedToInsertionPoint(false)
     , m_resetStyleInheritance(false)
 {
@@ -40,8 +40,8 @@ ElementResolveContext::ElementResolveContext(Element* element)
     m_distributedToInsertionPoint = parentDetails.insertionPoint();
     m_resetStyleInheritance = parentDetails.resetStyleInheritance();
 
-    Node* documentElement = document()->documentElement();
-    RenderStyle* documentStyle = document()->renderStyle();
+    Node* documentElement = document().documentElement();
+    RenderStyle* documentStyle = document().renderStyle();
     m_rootElementStyle = documentElement && element != documentElement ? documentElement->renderStyle() : documentStyle;
 }