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

content/renderer/scheduler/task_queue_manager.h

Index: content/renderer/scheduler/task_queue_manager.h
diff --git a/content/renderer/scheduler/task_queue_manager.h b/content/renderer/scheduler/task_queue_manager.h
index 3112e698157e47663322fe3e77415cd2f83c294b..a0a1a446b57be80efc3b7c8f20fa1c254b559c96 100644
--- a/content/renderer/scheduler/task_queue_manager.h
+++ b/content/renderer/scheduler/task_queue_manager.h
@@ -16,18 +16,11 @@
 #include "content/common/content_export.h"
 
 namespace base {
-namespace trace_event {
+namespace debug {
 class ConvertableToTraceFormat;
 class TracedValue;
 }
-
-// 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 debug {
-using ::base::trace_event::ConvertableToTraceFormat;
-using ::base::trace_event::TracedValue;
 }
-}  // namespace base
 
 namespace cc {
 class TestNowSource;