[presubmit] Enable readability/namespace linter checking.

src/zone-allocator.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_ZONE_ALLOCATOR_H_
 #define V8_ZONE_ALLOCATOR_H_
 
 #include <limits>
 
 #include "src/zone.h"
@@ skipping 48 matching lines @@
 
   Zone* zone() { return zone_; }
 
  private:
   zone_allocator();
   Zone* zone_;
 };
 
 typedef zone_allocator<bool> ZoneBoolAllocator;
 typedef zone_allocator<int> ZoneIntAllocator;
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_ZONE_ALLOCATOR_H_