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

Source/core/html/HTMLStyleElement.h

Index: Source/core/html/HTMLStyleElement.h
diff --git a/Source/core/html/HTMLStyleElement.h b/Source/core/html/HTMLStyleElement.h
index 27c0ca76b70d6fb7380cc871d7625f62f37b8a67..85980bfac2671873b54156701c89f1150796eb61 100644
--- a/Source/core/html/HTMLStyleElement.h
+++ b/Source/core/html/HTMLStyleElement.h
@@ -79,9 +79,9 @@ private:
     virtual void finishParsingChildren();
 
     virtual bool isLoading() const { return StyleElement::isLoading(); }
-    virtual bool sheetLoaded() { return StyleElement::sheetLoaded(document()); }
+    virtual bool sheetLoaded() { return StyleElement::sheetLoaded(&document()); }
     virtual void notifyLoadedSheetAndAllCriticalSubresources(bool errorOccurred);
-    virtual void startLoadingDynamicSheet() { StyleElement::startLoadingDynamicSheet(document()); }
+    virtual void startLoadingDynamicSheet() { StyleElement::startLoadingDynamicSheet(&document()); }
 
     virtual void addSubresourceAttributeURLs(ListHashSet<KURL>&) const;