[presubmit] Enable readability/namespace linter checking.

src/identity-map.h

 // Copyright 2015 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_IDENTITY_MAP_H_
 #define V8_IDENTITY_MAP_H_
 
 #include "src/handles.h"
 
 namespace v8 {
@@ skipping 74 matching lines @@
   // as the identity, returning:
   //    found => a pointer to the storage location for the value
   //    not found => {nullptr}
   V* Find(Handle<Object> key) { return reinterpret_cast<V*>(FindEntry(key)); }
 
   // Set the value for the given key.
   void Set(Handle<Object> key, V value) {
     *(reinterpret_cast<V*>(GetEntry(key))) = value;
   }
 };
-}
-}  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_IDENTITY_MAP_H_