Move Singleton and related structs to namespace base

net/tools/quic/quic_in_memory_cache.h

Index: net/tools/quic/quic_in_memory_cache.h
diff --git a/net/tools/quic/quic_in_memory_cache.h b/net/tools/quic/quic_in_memory_cache.h
index e10e02d1b2e6e07629df089d5a81429b5fdea80b..e96ad0107abe41c6fdaf7dec689ccdf8185cfd29 100644
--- a/net/tools/quic/quic_in_memory_cache.h
+++ b/net/tools/quic/quic_in_memory_cache.h
@@ -12,8 +12,12 @@
 #include "base/strings/string_piece.h"
 #include "net/spdy/spdy_framer.h"
 
+namespace base {
+
 template <typename Type> struct DefaultSingletonTraits;
 
+}  // namespace base
+
 namespace net {
 namespace tools {
 
@@ -99,7 +103,7 @@ class QuicInMemoryCache {
  private:
   typedef base::hash_map<std::string, Response*> ResponseMap;
 
-  friend struct DefaultSingletonTraits<QuicInMemoryCache>;
+  friend struct base::DefaultSingletonTraits<QuicInMemoryCache>;
   friend class test::QuicInMemoryCachePeer;
 
   QuicInMemoryCache();