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

base/trace_event/trace_event_synthetic_delay_unittest.cc

Index: base/trace_event/trace_event_synthetic_delay_unittest.cc
diff --git a/base/trace_event/trace_event_synthetic_delay_unittest.cc b/base/trace_event/trace_event_synthetic_delay_unittest.cc
index 84ac75cce79b17ee9b5b69b7c812f5b9dc58888c..1dc0fc26f5c7a1289a52e381e262e13c7f992fc9 100644
--- a/base/trace_event/trace_event_synthetic_delay_unittest.cc
+++ b/base/trace_event/trace_event_synthetic_delay_unittest.cc
@@ -7,7 +7,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
-namespace debug {
+namespace trace_event {
 namespace {
 
 const int kTargetDurationMs = 100;
@@ -150,5 +150,5 @@ TEST_F(TraceEventSyntheticDelayTest, BeginParallel) {
   EXPECT_LT((Now() - start_time).InMilliseconds(), kShortDurationMs);
 }
 
-}  // namespace debug
+}  // namespace trace_event
 }  // namespace base