Move Singleton and related structs to namespace base

base/trace_event/trace_event_etw_export_win.h

Index: base/trace_event/trace_event_etw_export_win.h
diff --git a/base/trace_event/trace_event_etw_export_win.h b/base/trace_event/trace_event_etw_export_win.h
index c1eafffa3a69ece14852aa1a18ff5ef4931b236d..7e70121fd21f671a0a4903630b8c1586b26c2d5e 100644
--- a/base/trace_event/trace_event_etw_export_win.h
+++ b/base/trace_event/trace_event_etw_export_win.h
@@ -13,10 +13,10 @@
 #include "base/trace_event/trace_event_impl.h"
 
 // Fwd.
+namespace base {
 template <typename Type>
 struct StaticMemorySingletonTraits;
 
-namespace base {
 namespace trace_event {
 
 class BASE_EXPORT TraceEventETWExport {
@@ -66,7 +66,7 @@ class BASE_EXPORT TraceEventETWExport {
 
  private:
   // Ensure only the provider can construct us.
-  friend struct StaticMemorySingletonTraits<TraceEventETWExport>;
+  friend struct base::StaticMemorySingletonTraits<TraceEventETWExport>;
   // To have access to UpdateKeyword().
   class ETWKeywordUpdateThread;
   TraceEventETWExport();