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..25f4656f7ada72bceb2c50d39e626f8e53729e02 100644
--- a/content/browser/tracing/etw_system_event_consumer_win.h
+++ b/content/browser/tracing/etw_system_event_consumer_win.h
@@ -12,8 +12,10 @@
 #include "base/win/event_trace_consumer.h"
 #include "base/win/event_trace_controller.h"
 
+namespace base {
 template <typename Type>
 struct DefaultSingletonTraits;
+}
 
 namespace content {
 
@@ -32,7 +34,7 @@ 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();