[presubmit] Enable readability/namespace linter checking.

src/base/platform/condition-variable.cc

 // Copyright 2013 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.
 
 #include "src/base/platform/condition-variable.h"
 
 #include <errno.h>
 #include <time.h>
 
 #include "src/base/platform/time.h"
@@ skipping 295 matching lines @@
 
   // Release the wait event.
   DCHECK(!result || event->notified_);
   native_handle_.Post(event, result);
 
   return result;
 }
 
 #endif  // V8_OS_POSIX
 
-} }  // namespace v8::base
+}  // namespace base
+}  // namespace v8