Move Singleton and related structs to namespace base

chrome/browser/local_discovery/privet_url_fetcher.cc

Index: chrome/browser/local_discovery/privet_url_fetcher.cc
diff --git a/chrome/browser/local_discovery/privet_url_fetcher.cc b/chrome/browser/local_discovery/privet_url_fetcher.cc
index 390fb8350425fcddb07cfe50a48d5b6029d2151d..55e9506406c2237b5bb8a2d257cb10899a3df453 100644
--- a/chrome/browser/local_discovery/privet_url_fetcher.cc
+++ b/chrome/browser/local_discovery/privet_url_fetcher.cc
@@ -30,7 +30,7 @@ typedef std::map<std::string, std::string> TokenMap;
 struct TokenMapHolder {
  public:
   static TokenMapHolder* GetInstance() {
-    return Singleton<TokenMapHolder>::get();
+    return base::Singleton<TokenMapHolder>::get();
   }
 
   TokenMap map;