[presubmit] Enable readability/namespace linter checking.

src/fixed-dtoa.h

 // Copyright 2010 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_FIXED_DTOA_H_
 #define V8_FIXED_DTOA_H_
 
 #include "src/vector.h"
 
 namespace v8 {
@@ skipping 11 matching lines @@
 // Halfway cases are rounded towards +/-Infinity (away from 0). The call
 // FastFixedDtoa(0.15, 2, ...) thus returns buffer = "2", decimal_point = 0.
 // The returned buffer may contain digits that would be truncated from the
 // shortest representation of the input.
 //
 // This method only works for some parameters. If it can't handle the input it
 // returns false. The output is null-terminated when the function succeeds.
 bool FastFixedDtoa(double v, int fractional_count,
                    Vector<char> buffer, int* length, int* decimal_point);
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_FIXED_DTOA_H_