diff --git a/src/data-flow.h b/src/data-flow.h
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+// Copyright 2010 the V8 project authors. 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
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_DATAFLOW_H_
+#define V8_DATAFLOW_H_
+
+#include "ast.h"
+#include "scopes.h"
+
+namespace v8 {
+namespace internal {
+
+// This class is used to number all expressions in the AST according to
+// their evaluation order (post-order left-to-right traversal).
+class AstLabeler: public AstVisitor {
+ public:
+  AstLabeler() : next_number_(0), has_this_properties_(false) {}
+
+  void Label(FunctionLiteral* fun);
+
+  bool has_this_properties() { return has_this_properties_; }
+
+ private:
+  void VisitDeclarations(ZoneList<Declaration*>* decls);
+  void VisitStatements(ZoneList<Statement*>* stmts);
+
+  // AST node visit functions.
+#define DECLARE_VISIT(type) virtual void Visit##type(type* node);
+  AST_NODE_LIST(DECLARE_VISIT)
+#undef DECLARE_VISIT
+
+  // Traversal number for labelling AST nodes.
+  int next_number_;
+
+  bool has_this_properties_;
+
+  DISALLOW_COPY_AND_ASSIGN(AstLabeler);
+};
+
+
+} }  // namespace v8::internal
+
+#endif  // V8_DATAFLOW_H_