Update from https://crrev.com/316786

base/trace_event/trace_event.h

Index: base/trace_event/trace_event.h
diff --git a/base/trace_event/trace_event.h b/base/trace_event/trace_event.h
index c8583d73449cbc0dd47d6df74c8c331e81f4e1ae..07a2afac858ec34f9105e40217dd23b659ec6d60 100644
--- a/base/trace_event/trace_event.h
+++ b/base/trace_event/trace_event.h
@@ -1603,12 +1603,4 @@ template<typename IDType> class TraceScopedTrackableObject {
 }  // namespace trace_event
 }  // namespace base
 
-// TODO(ssid): remove these aliases after the tracing clients are moved to the
-// new trace_event namespace. See crbug.com/451032. ETA: March 2015.
-namespace base {
-namespace debug {
-using base::trace_event::TraceScopedTrackableObject;
-}  // namespace debug
-}  // namespace base
-
 #endif /* BASE_TRACE_EVENT_TRACE_EVENT_H_ */