Enable clang warning for ignored attributes.

components/login/base_screen_handler_utils.h

 // Copyright (c) 2013 The Chromium 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 COMPONENTS_LOGIN_BASE_SCREEN_HANDLER_UTILS_H_
 #define COMPONENTS_LOGIN_BASE_SCREEN_HANDLER_UTILS_H_
 
 #include <cstddef>
 #include <string>
 
 #include "base/callback.h"
 #include "base/logging.h"
 #include "base/strings/string16.h"
 #include "base/tuple.h"
 #include "base/values.h"
 #include "components/login/login_export.h"
 
 namespace login {
 
 typedef std::vector<std::string> StringList;
 typedef std::vector<base::string16> String16List;
 
 template <typename T>
 struct LOGIN_EXPORT UnwrapConstRef {
   typedef T Type;
 };
 
 template <typename T>
-struct LOGIN_EXPORT UnwrapConstRef<const T&> {
+struct UnwrapConstRef<const T&> {
   typedef T Type;
 };
 
 bool LOGIN_EXPORT ParseValue(const base::Value* value, bool* out_value);
 bool LOGIN_EXPORT ParseValue(const base::Value* value, int* out_value);
 bool LOGIN_EXPORT ParseValue(const base::Value* value, double* out_value);
 bool LOGIN_EXPORT ParseValue(const base::Value* value, std::string* out_value);
 bool LOGIN_EXPORT
     ParseValue(const base::Value* value, base::string16* out_value);
 bool LOGIN_EXPORT ParseValue(const base::Value* value,
@@ skipping 41 matching lines @@
 void CallbackWrapper(const base::Callback<void(Args...)>& callback,
                      const base::ListValue* args) {
   DispatchToCallback(callback, args,
                      base::MakeIndexSequence<sizeof...(Args)>());
 }
 
 
 }  // namespace login
 
 #endif  // COMPONENTS_LOGIN_BASE_SCREEN_HANDLER_UTILS_H_