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

Source/core/xml/XSLStyleSheetLibxslt.cpp

Index: Source/core/xml/XSLStyleSheetLibxslt.cpp
diff --git a/Source/core/xml/XSLStyleSheetLibxslt.cpp b/Source/core/xml/XSLStyleSheetLibxslt.cpp
index 15e8a66ae75b372d450f9e0feca92587b8e948a8..b7b8326694016aaec46e0d498b4d17aaa4424043 100644
--- a/Source/core/xml/XSLStyleSheetLibxslt.cpp
+++ b/Source/core/xml/XSLStyleSheetLibxslt.cpp
@@ -254,7 +254,7 @@ Document* XSLStyleSheet::ownerDocument()
     for (XSLStyleSheet* styleSheet = this; styleSheet; styleSheet = styleSheet->parentStyleSheet()) {
         Node* node = styleSheet->ownerNode();
         if (node)
-            return node->document();
+            return &node->document();
     }
     return 0;
 }