[presubmit] Enable readability/namespace linter checking.

src/debug/debug.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.
 
 #ifndef V8_DEBUG_DEBUG_H_
 #define V8_DEBUG_DEBUG_H_
 
 #include "src/allocation.h"
 #include "src/arguments.h"
 #include "src/assembler.h"
@@ skipping 745 matching lines @@
 
 
   static void GenerateSlot(MacroAssembler* masm, RelocInfo::Mode mode,
                            int call_argc = -1);
 
   static void PatchDebugBreakSlot(Address pc, Handle<Code> code);
   static void ClearDebugBreakSlot(Address pc);
 };
 
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_DEBUG_DEBUG_H_