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

src/ast-numbering.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/ast.h"
 #include "src/ast-numbering.h"
 #include "src/compiler.h"
 #include "src/scopes.h"
 
 namespace v8 {
 namespace internal {
 
 
 class AstNumberingVisitor FINAL : public AstVisitor {
  public:
   explicit AstNumberingVisitor(Zone* zone)
       : AstVisitor(), next_id_(BailoutId::FirstUsable().ToInt()) {
     InitializeAstVisitor(zone);
   }
 
   void Renumber(FunctionLiteral* node);
 
  private:
 // AST node visitor interface.
-#define DEFINE_VISIT(type) virtual void Visit##type(type* node);
+#define DEFINE_VISIT(type) virtual void Visit##type(type* node) OVERRIDE;
   AST_NODE_LIST(DEFINE_VISIT)
 #undef DEFINE_VISIT
 
-  void VisitStatements(ZoneList<Statement*>* statements);
-  void VisitDeclarations(ZoneList<Declaration*>* declarations);
+  void VisitStatements(ZoneList<Statement*>* statements) OVERRIDE;
+  void VisitDeclarations(ZoneList<Declaration*>* declarations) OVERRIDE;
   void VisitArguments(ZoneList<Expression*>* arguments);
   void VisitObjectLiteralProperty(ObjectLiteralProperty* property);
 
   int ReserveIdRange(int n) {
     int tmp = next_id_;
     next_id_ += n;
     return tmp;
   }
 
   void IncrementNodeCount() { properties_.add_node_count(1); }
@@ skipping 427 matching lines @@
 }
 
 
 bool AstNumbering::Renumber(FunctionLiteral* function, Zone* zone) {
   AstNumberingVisitor visitor(zone);
   visitor.Renumber(function);
   return !visitor.HasStackOverflow();
 }
 }
 }  // namespace v8::internal