[presubmit] Enable readability/namespace linter checking.

src/flags.h

 // Copyright 2006-2008 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.
 
 #ifndef V8_FLAGS_H_
 #define V8_FLAGS_H_
 
 #include "src/globals.h"
 
 namespace v8 {
@@ skipping 45 matching lines @@
   static void PrintHelp();
 
   // Set flags as consequence of being implied by another flag.
   static void EnforceFlagImplications();
 
   // Hash of flags (to quickly determine mismatching flag expectations).
   // This hash is calculated during V8::Initialize and cached.
   static uint32_t Hash();
 };
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_FLAGS_H_