Move Singleton and related structs to namespace base

chrome/browser/extensions/api/notifications/notifications_api.cc

Index: chrome/browser/extensions/api/notifications/notifications_api.cc
diff --git a/chrome/browser/extensions/api/notifications/notifications_api.cc b/chrome/browser/extensions/api/notifications/notifications_api.cc
index 788c41eb1e05d06a419a11cfc6ed4d53b40ae9cf..ba47fa4f89e7e4e89c5e854158ee7615f8b6f099 100644
--- a/chrome/browser/extensions/api/notifications/notifications_api.cc
+++ b/chrome/browser/extensions/api/notifications/notifications_api.cc
@@ -106,11 +106,11 @@ class ShutdownNotifierFactory
     : public BrowserContextKeyedServiceShutdownNotifierFactory {
  public:
   static ShutdownNotifierFactory* GetInstance() {
-    return Singleton<ShutdownNotifierFactory>::get();
+    return base::Singleton<ShutdownNotifierFactory>::get();
   }
 
  private:
-  friend struct DefaultSingletonTraits<ShutdownNotifierFactory>;
+  friend struct base::DefaultSingletonTraits<ShutdownNotifierFactory>;
 
   ShutdownNotifierFactory()
       : BrowserContextKeyedServiceShutdownNotifierFactory(