Drop [LegacyImplementedInBaseClass] from ChildNode IDL interface

Source/core/dom/ChildNode.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ChildNode_h
+#define ChildNode_h
+
+#include "core/dom/ElementTraversal.h"
+#include "core/dom/Node.h"
+
+namespace WebCore {
+
+class ChildNode {
+public:
+    static Element* previousElementSibling(Node* node)
+    {
+        ASSERT(node);
+        return ElementTraversal::previousSibling(*node);
+    }
+
+    static Element* nextElementSibling(Node* node)
+    {
+        ASSERT(node);
+        return ElementTraversal::nextSibling(*node);
+    }
+
+    static void remove(Node* node, ExceptionState& exceptionState)
+    {
+        ASSERT(node);
+        return node->remove(exceptionState);
+    }
+};
+
+} // namespace WebCore
+
+#endif // ChildNode_h