[presubmit] Enable readability/namespace linter checking.

src/base/macros.h

 // Copyright 2014 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_BASE_MACROS_H_
 #define V8_BASE_MACROS_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 399 matching lines @@
 // which requires C++11. Switch to std::is_fundamental once possible.
 template <typename T>
 inline bool is_fundamental() {
   return false;
 }
 
 template <>
 inline bool is_fundamental<uint8_t>() {
   return true;
 }
-}
-}  // namespace v8::base
+
+}  // namespace base
+}  // namespace v8
 
 #endif   // V8_BASE_MACROS_H_