[presubmit] Enable readability/namespace linter checking.

src/base/platform/elapsed-timer.h

 // Copyright 2013 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_PLATFORM_ELAPSED_TIMER_H_
 #define V8_BASE_PLATFORM_ELAPSED_TIMER_H_
 
 #include "src/base/logging.h"
 #include "src/base/platform/time.h"
 
@@ skipping 74 matching lines @@
     DCHECK(!now.IsNull());
     return now;
   }
 
   TimeTicks start_ticks_;
 #ifdef DEBUG
   bool started_;
 #endif
 };
 
-} }  // namespace v8::base
+}  // namespace base
+}  // namespace v8
 
 #endif  // V8_BASE_PLATFORM_ELAPSED_TIMER_H_