[presubmit] Enable readability/namespace linter checking.

src/base/atomicops_internals_x86_gcc.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.
 
 // This file is an internal atomic implementation, use atomicops.h instead.
 
 #ifndef V8_BASE_ATOMICOPS_INTERNALS_X86_GCC_H_
 #define V8_BASE_ATOMICOPS_INTERNALS_X86_GCC_H_
 
 namespace v8 {
@@ skipping 249 matching lines @@
 }
 
 inline Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,
                                        Atomic64 old_value,
                                        Atomic64 new_value) {
   return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
 }
 
 #endif  // defined(__x86_64__)
 
-} }  // namespace v8::base
+}  // namespace base
+}  // namespace v8
 
 #undef ATOMICOPS_COMPILER_BARRIER
 
 #endif  // V8_BASE_ATOMICOPS_INTERNALS_X86_GCC_H_