Move Singleton and related structs to namespace base

components/tracing/trace_config_file.cc

Index: components/tracing/trace_config_file.cc
diff --git a/components/tracing/trace_config_file.cc b/components/tracing/trace_config_file.cc
index e1cbc5c391e6c98edda8f907a91c53e9d39b7e81..796eb1b7cb5dae5c923ddef43b1589cdd26eb243 100644
--- a/components/tracing/trace_config_file.cc
+++ b/components/tracing/trace_config_file.cc
@@ -41,8 +41,8 @@ const char kResultFileParam[] = "result_file";
 } // namespace
 
 TraceConfigFile* TraceConfigFile::GetInstance() {
-  return Singleton<TraceConfigFile,
-                   DefaultSingletonTraits<TraceConfigFile>>::get();
+  return base::Singleton<TraceConfigFile,
+                         base::DefaultSingletonTraits<TraceConfigFile>>::get();
 }
 
 TraceConfigFile::TraceConfigFile()