[presubmit] Enable readability/namespace linter checking.

src/hydrogen-mark-deoptimize.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_MARK_DEOPTIMIZE_H_
 #define V8_HYDROGEN_MARK_DEOPTIMIZE_H_
 
 #include "src/hydrogen.h"
 
 namespace v8 {
@@ skipping 29 matching lines @@
   explicit HComputeChangeUndefinedToNaN(HGraph* graph)
       : HPhase("H_Compute change undefined to nan", graph) {}
 
   void Run();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(HComputeChangeUndefinedToNaN);
 };
 
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_HYDROGEN_MARK_DEOPTIMIZE_H_