Move Singleton and related structs to namespace base

content/browser/tracing/etw_system_event_consumer_win.h

Index: content/browser/tracing/etw_system_event_consumer_win.h
diff --git a/content/browser/tracing/etw_system_event_consumer_win.h b/content/browser/tracing/etw_system_event_consumer_win.h
index 3611bee7c6037560cb65dad4c9f62a6f79267dc6..8fe1e2e2ff0cd4bb936387ce3c5a7bf60fceaef5 100644
--- a/content/browser/tracing/etw_system_event_consumer_win.h
+++ b/content/browser/tracing/etw_system_event_consumer_win.h
@@ -13,7 +13,7 @@
 #include "base/win/event_trace_controller.h"
 
 template <typename Type>
-struct DefaultSingletonTraits;
+struct base::DefaultSingletonTraits;
 
 namespace content {
 
@@ -32,7 +32,7 @@ class EtwSystemEventConsumer :
  private:
   // This allows constructor and destructor to be private and usable only
   // by the Singleton class.
-  friend struct DefaultSingletonTraits<EtwSystemEventConsumer>;
+  friend struct base::DefaultSingletonTraits<EtwSystemEventConsumer>;
 
   // Constructor.
   EtwSystemEventConsumer();