[presubmit] Enable readability/namespace linter checking.

src/string-stream.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_STRING_STREAM_H_
 #define V8_STRING_STREAM_H_
 
 #include "src/allocation.h"
 #include "src/base/smart-pointers.h"
 #include "src/handles.h"
@@ skipping 160 matching lines @@
   unsigned capacity_;
   unsigned length_;  // does not include terminating 0-character
   char* buffer_;
 
   bool full() const { return (capacity_ - length_) == 1; }
   int space() const { return capacity_ - length_; }
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(StringStream);
 };
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_STRING_STREAM_H_