[presubmit] Enable readability/namespace linter checking.

src/base/once.h

 // Copyright 2012 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.
 
 // emulates google3/base/once.h
 //
 // This header is intended to be included only by v8's internal code. Users
 // should not use this directly.
 //
 // This is basically a portable version of pthread_once().
@@ skipping 79 matching lines @@
 
 template <typename Arg>
 inline void CallOnce(OnceType* once,
     typename OneArgFunction<Arg*>::type init_func, Arg* arg) {
   if (Acquire_Load(once) != ONCE_STATE_DONE) {
     CallOnceImpl(once, reinterpret_cast<PointerArgFunction>(init_func),
         static_cast<void*>(arg));
   }
 }
 
-} }  // namespace v8::base
+}  // namespace base
+}  // namespace v8
 
 #endif  // V8_BASE_ONCE_H_