[presubmit] Enable readability/namespace linter checking.

src/dtoa.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_DTOA_H_
 #define V8_DTOA_H_
 
 #include "src/vector.h"
 
 namespace v8 {
@@ skipping 41 matching lines @@
 //   'requested_digits', the function is allowed to return fewer digits, in
 //   which case the caller has to fill the missing digits with '0's.
 //   Halfway cases are again rounded away from 0.
 // 'DoubleToAscii' expects the given buffer to be big enough to hold all digits
 // and a terminating null-character. In SHORTEST-mode it expects a buffer of
 // at least kBase10MaximalLength + 1. Otherwise, the size of the output is
 // limited to requested_digits digits plus the null terminator.
 void DoubleToAscii(double v, DtoaMode mode, int requested_digits,
                    Vector<char> buffer, int* sign, int* length, int* point);
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_DTOA_H_