[presubmit] Enable readability/namespace linter checking.

src/hydrogen-dce.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_DCE_H_
 #define V8_HYDROGEN_DCE_H_
 
 #include "src/hydrogen.h"
 
 namespace v8 {
@@ skipping 11 matching lines @@
   }
 
  private:
   void MarkLive(HValue* instr, ZoneList<HValue*>* worklist);
   void PrintLive(HValue* ref, HValue* instr);
   void MarkLiveInstructions();
   void RemoveDeadInstructions();
 };
 
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_HYDROGEN_DCE_H_