[presubmit] Enable readability/namespace linter checking.

src/bootstrapper.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_BOOTSTRAPPER_H_
 #define V8_BOOTSTRAPPER_H_
 
 #include "src/factory.h"
 
 namespace v8 {
@@ skipping 158 matching lines @@
   NativesExternalStringResource(const char* source, size_t length)
       : data_(source), length_(length) {}
   const char* data() const override { return data_; }
   size_t length() const override { return length_; }
 
  private:
   const char* data_;
   size_t length_;
 };
 
-}}  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_BOOTSTRAPPER_H_