[presubmit] Enable readability/namespace linter checking.

test/cctest/test-identity-map.cc

 // Copyright 2015 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/v8.h"
 
 #include "src/identity-map.h"
 #include "src/zone.h"
 
 #include "test/cctest/cctest.h"
@@ skipping 317 matching lines @@
 
   // Do an explicit, real GC.
   t.heap()->CollectGarbage(i::NEW_SPACE);
 
   // Check that searching for the numbers finds the same values.
   for (size_t i = 0; i < arraysize(num_keys); i++) {
     t.CheckFind(num_keys[i], &num_keys[i]);
     t.CheckGet(num_keys[i], &num_keys[i]);
   }
 }
-}
-}
+
+}  // namespace internal
+}  // namespace v8