[presubmit] Enable readability/namespace linter checking.

src/ppc/lithium-codegen-ppc.h

 // Copyright 2014 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_PPC_LITHIUM_CODEGEN_PPC_H_
 #define V8_PPC_LITHIUM_CODEGEN_PPC_H_
 
 #include "src/ppc/lithium-ppc.h"
 
 #include "src/ppc/lithium-gap-resolver-ppc.h"
@@ skipping 340 matching lines @@
   LCodeGen* codegen() const { return codegen_; }
   MacroAssembler* masm() const { return codegen_->masm(); }
 
  private:
   LCodeGen* codegen_;
   Label entry_;
   Label exit_;
   Label* external_exit_;
   int instruction_index_;
 };
-}
-}  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_PPC_LITHIUM_CODEGEN_PPC_H_