Move Singleton and related structs to namespace base

base/trace_event/trace_log.cc

Index: base/trace_event/trace_log.cc
diff --git a/base/trace_event/trace_log.cc b/base/trace_event/trace_log.cc
index f6c9115646314f6ca7e3e048fa1fda56148d30cd..f84feb5217c3fbabc59888a3acd39fc30da10bed 100644
--- a/base/trace_event/trace_log.cc
+++ b/base/trace_event/trace_log.cc
@@ -39,18 +39,20 @@
 #include "base/trace_event/trace_event_win.h"
 #endif
 
+// The thread buckets for the sampling profiler.
+BASE_EXPORT TRACE_EVENT_API_ATOMIC_WORD g_trace_state[3];
+
+namespace base {
+
 class DeleteTraceLogForTesting {
  public:
   static void Delete() {
-    Singleton<base::trace_event::TraceLog,
-              LeakySingletonTraits<base::trace_event::TraceLog>>::OnExit(0);
+    base::Singleton<
+        trace_event::TraceLog,
+        LeakySingletonTraits<base::trace_event::TraceLog>>::OnExit(0);
   }
 };
 
-// The thread buckets for the sampling profiler.
-BASE_EXPORT TRACE_EVENT_API_ATOMIC_WORD g_trace_state[3];
-
-namespace base {
 namespace trace_event {
 
 namespace {
@@ -395,7 +397,7 @@ TraceLogStatus::~TraceLogStatus() {}
 
 // static
 TraceLog* TraceLog::GetInstance() {
-  return Singleton<TraceLog, LeakySingletonTraits<TraceLog>>::get();
+  return base::Singleton<TraceLog, base::LeakySingletonTraits<TraceLog>>::get();
 }
 
 TraceLog::TraceLog()