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

Source/core/svg/SVGElementRareData.h

Index: Source/core/svg/SVGElementRareData.h
diff --git a/Source/core/svg/SVGElementRareData.h b/Source/core/svg/SVGElementRareData.h
index fe3dcbad1f6174ffe60aba259bf177900b3f5dd8..6f3b38da8d134059b54262e2ce5d9d33d4fe2b76 100644
--- a/Source/core/svg/SVGElementRareData.h
+++ b/Source/core/svg/SVGElementRareData.h
@@ -94,7 +94,7 @@ public:
             return 0;
         if (!m_overrideComputedStyle || m_needsOverrideComputedStyleUpdate) {
             // The style computed here contains no CSS Animations/Transitions or SMIL induced rules - this is needed to compute the "base value" for the SMIL animation sandwhich model.
-            m_overrideComputedStyle = element->document()->styleResolver()->styleForElement(element, parentStyle, DisallowStyleSharing, MatchAllRulesExcludingSMIL);
+            m_overrideComputedStyle = element->document().styleResolver()->styleForElement(element, parentStyle, DisallowStyleSharing, MatchAllRulesExcludingSMIL);
             m_needsOverrideComputedStyleUpdate = false;
         }
         ASSERT(m_overrideComputedStyle);