Add a few missing overrides found by a new clang warning.

src/rewriter.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/rewriter.h"
 
 #include "src/ast.h"
 #include "src/compiler.h"
@@ skipping 42 matching lines @@
 
   Expression* SetResult(Expression* value) {
     result_assigned_ = true;
     VariableProxy* result_proxy = factory()->NewVariableProxy(result_);
     return factory()->NewAssignment(
         Token::ASSIGN, result_proxy, value, RelocInfo::kNoPosition);
   }
 
   // Node visitors.
 #define DEF_VISIT(type) \
-  virtual void Visit##type(type* node);
+  virtual void Visit##type(type* node) OVERRIDE;
   AST_NODE_LIST(DEF_VISIT)
 #undef DEF_VISIT
 
   void VisitIterationStatement(IterationStatement* stmt);
 
   DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
 };
 
 
 void Processor::Process(ZoneList<Statement*>* statements) {
@@ skipping 183 matching lines @@
           processor.factory()->NewReturnStatement(result_proxy, pos);
       body->Add(result_statement, info->zone());
     }
   }
 
   return true;
 }
 
 
 } }  // namespace v8::internal