[presubmit] Enable readability/namespace linter checking.

src/v8.h

 // Copyright 2011 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_V8_H_
 #define V8_V8_H_
 
 #include "include/v8.h"
 #include "src/allocation.h"
 
@@ skipping 23 matching lines @@
   static void SetSnapshotBlob(StartupData* snapshot_blob);
 
  private:
   static void InitializeOncePerProcessImpl();
   static void InitializeOncePerProcess();
 
   // v8::Platform to use.
   static v8::Platform* platform_;
 };
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_V8_H_