Move Singleton and related structs to namespace base

components/wifi_sync/wifi_credential_syncable_service_factory.h

Index: components/wifi_sync/wifi_credential_syncable_service_factory.h
diff --git a/components/wifi_sync/wifi_credential_syncable_service_factory.h b/components/wifi_sync/wifi_credential_syncable_service_factory.h
index be5b6c506a21fe68cd47f44c6e88857e66f04d2e..c006cb3d8ccd8d3453906d2767af56f6e5b5ef98 100644
--- a/components/wifi_sync/wifi_credential_syncable_service_factory.h
+++ b/components/wifi_sync/wifi_credential_syncable_service_factory.h
@@ -41,7 +41,8 @@ class WifiCredentialSyncableServiceFactory
 #endif
 
  private:
-  friend struct DefaultSingletonTraits<WifiCredentialSyncableServiceFactory>;
+  friend struct base::DefaultSingletonTraits<
+      WifiCredentialSyncableServiceFactory>;
 
   WifiCredentialSyncableServiceFactory();
   ~WifiCredentialSyncableServiceFactory() override;