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

cc/scheduler/scheduler_settings.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_SCHEDULER_SCHEDULER_SETTINGS_H_
 #define CC_SCHEDULER_SCHEDULER_SETTINGS_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 #include "base/values.h"
 #include "cc/base/cc_export.h"
 
 namespace base {
-namespace trace_event {
+namespace debug {
 class ConvertableToTraceFormat;
 }
-
-// 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;
 }
-}  // namespace base
 
 namespace cc {
 class LayerTreeSettings;
 
 class CC_EXPORT SchedulerSettings {
  public:
   SchedulerSettings();
   explicit SchedulerSettings(const LayerTreeSettings& settings);
   ~SchedulerSettings();
 
@@ skipping 14 matching lines @@
   bool main_thread_should_always_be_low_latency;
 
   base::TimeDelta background_frame_interval;
 
   scoped_refptr<base::debug::ConvertableToTraceFormat> AsValue() const;
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_SCHEDULER_SETTINGS_H_