Move Singleton and related structs to namespace base

chrome/browser/chromeos/login/easy_unlock/easy_unlock_tpm_key_manager_factory.h

 // Copyright 2014 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 CHROME_BROWSER_CHROMEOS_LOGIN_EASY_UNLOCK_EASY_UNLOCK_TPM_KEY_MANAGER_FACTORY_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_EASY_UNLOCK_EASY_UNLOCK_TPM_KEY_MANAGER_FACTORY_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 namespace content {
 class BrowserContext;
 }
 
-template <typename T> struct DefaultSingletonTraits;
+namespace base {
+template <typename T>
+struct DefaultSingletonTraits;
+}  // namespace base
+
 class EasyUnlockTpmKeyManager;
 
 // Singleton factory that builds and owns all EasyUnlockTpmKeyManager services.
 class EasyUnlockTpmKeyManagerFactory
     : public BrowserContextKeyedServiceFactory {
  public:
   static EasyUnlockTpmKeyManagerFactory* GetInstance();
 
   static EasyUnlockTpmKeyManager* Get(content::BrowserContext* context);
   static EasyUnlockTpmKeyManager* GetForUser(const std::string& user_id);
 
  private:
-  friend struct DefaultSingletonTraits<EasyUnlockTpmKeyManagerFactory>;
+  friend struct base::DefaultSingletonTraits<EasyUnlockTpmKeyManagerFactory>;
 
   EasyUnlockTpmKeyManagerFactory();
   ~EasyUnlockTpmKeyManagerFactory() override;
 
   // BrowserContextKeyedServiceFactory:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
   content::BrowserContext* GetBrowserContextToUse(
       content::BrowserContext* context) const override;
 
   DISALLOW_COPY_AND_ASSIGN(EasyUnlockTpmKeyManagerFactory);
 };
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_EASY_UNLOCK_EASY_UNLOCK_TPM_KEY_MANAGER_FACTORY_H_