[presubmit] Enable readability/namespace linter checking.

test/cctest/heap-tester.h

 // 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.
 
 #ifndef HEAP_TESTER_H_
 #define HEAP_TESTER_H_
 
 #include "src/handles.h"
 #include "src/heap/spaces.h"
 
@@ skipping 35 matching lines @@
   HEAP_TEST_METHODS(DECLARE_STATIC)
 #undef HEAP_TEST_METHODS
 
   /* test-alloc.cc */
   static AllocationResult AllocateAfterFailures();
   static Handle<Object> TestAllocateAfterFailures();
 
   /* test-api.cc */
   static void ResetWeakHandle(bool global_gc);
 };
-}
-}
+
+}  // namespace internal
+}  // namespace v8
 
 #endif  // HEAP_TESTER_H_