Fix Document leak from NodeFilter.

Source/core/dom/Document.idl

 /*
  * Copyright (C) 2006, 2007, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006, 2007 Samuel Weinig <sam@webkit.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 57 matching lines @@
     [RaisesException] Event              createEvent([Default=Undefined] optional DOMString eventType);
 
     // DOM Level 2 Traversal and Range (DocumentRange interface)
 
     Range              createRange();
 
     // DOM Level 2 Traversal and Range (DocumentTraversal interface)
     // In DOM4, the fourth argument |expandEntityReferences| is removed.
     // Historically, this argument was never implemented and has been ignored.
     // We still receive the argument to keep compatibility, but don't do anything if it's specified.
-    [RaisesException] NodeIterator createNodeIterator(Node root,
-                                                      optional unsigned long whatToShow,
-                                                      optional NodeFilter filter,
-                                                      optional boolean expandEntityReferences);
-    [RaisesException] TreeWalker createTreeWalker(Node root,
-                                                  optional unsigned long whatToShow,
-                                                  optional NodeFilter filter,
-                                                  optional boolean expandEntityReferences);
+    [Custom, RaisesException] NodeIterator createNodeIterator(Node root,
+                                                              optional unsigned long whatToShow,
+                                                              optional NodeFilter filter,
+                                                              optional boolean expandEntityReferences);
+    [Custom, RaisesException] TreeWalker createTreeWalker(Node root,
+                                                          optional unsigned long whatToShow,
+                                                          optional NodeFilter filter,
+                                                          optional boolean expandEntityReferences);
 
     // DOM Level 2 Abstract Views (DocumentView interface)
 
     readonly attribute Window defaultView;
 
     // DOM Level 2 Style (DocumentStyle interface)
 
     readonly attribute StyleSheetList styleSheets;
 
     // DOM Level 2 Style (DocumentCSS interface)
@@ skipping 176 matching lines @@
     readonly attribute boolean webkitHidden;
 
     // Security Policy API: http://dvcs.w3.org/hg/content-security-policy/raw-file/tip/csp-specification.dev.html#script-interfaces
     [EnabledAtRuntime=experimentalContentSecurityPolicyFeatures] readonly attribute SecurityPolicy securityPolicy;
 
     readonly attribute HTMLScriptElement currentScript;
 };
 
 Document implements ParentNode;