[presubmit] Enable readability/namespace linter checking.

src/hydrogen-gvn.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_HYDROGEN_GVN_H_
 #define V8_HYDROGEN_GVN_H_
 
 #include <iosfwd>
 
 #include "src/hydrogen.h"
@@ skipping 130 matching lines @@
   // A map of loop header block IDs to their loop's side effects.
   ZoneList<SideEffects> loop_side_effects_;
 
   // Used when collecting side effects on paths from dominator to
   // dominated.
   BitVector visited_on_paths_;
 
   DISALLOW_COPY_AND_ASSIGN(HGlobalValueNumberingPhase);
 };
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_HYDROGEN_GVN_H_