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

Source/bindings/v8/BindingSecurity.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 73 matching lines @@
     return target && canAccessDocument(target->document(), reportingOption);
 }
 
 bool BindingSecurity::shouldAllowAccessToFrame(Frame* target, ExceptionState& es)
 {
     return target && canAccessDocument(target->document(), es);
 }
 
 bool BindingSecurity::shouldAllowAccessToNode(Node* target)
 {
-    return target && canAccessDocument(target->document());
+    return target && canAccessDocument(&target->document());
 }
 
 }