Reland of Move tracing namespace from base::debug to base::trace_event.

base/trace_event/trace_event_impl.cc

Index: base/trace_event/trace_event_impl.cc
diff --git a/base/trace_event/trace_event_impl.cc b/base/trace_event/trace_event_impl.cc
index a8a0cc1a011dd71248dc92f6f8c18ea8de5aa157..95cf06d5a576c061eda861c74f923de6c50b9eef 100644
--- a/base/trace_event/trace_event_impl.cc
+++ b/base/trace_event/trace_event_impl.cc
@@ -41,8 +41,8 @@
 class DeleteTraceLogForTesting {
  public:
   static void Delete() {
-    Singleton<base::debug::TraceLog,
-              LeakySingletonTraits<base::debug::TraceLog> >::OnExit(0);
+    Singleton<base::trace_event::TraceLog,
+              LeakySingletonTraits<base::trace_event::TraceLog>>::OnExit(0);
   }
 };
 
@@ -50,7 +50,7 @@ class DeleteTraceLogForTesting {
 BASE_EXPORT TRACE_EVENT_API_ATOMIC_WORD g_trace_state[3];
 
 namespace base {
-namespace debug {
+namespace trace_event {
 
 namespace {
 
@@ -2560,7 +2560,7 @@ const CategoryFilter::StringList&
   return delays_;
 }
 
-}  // namespace debug
+}  // namespace trace_event
 }  // namespace base
 
 namespace trace_event_internal {