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

cc/output/begin_frame_args.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_OUTPUT_BEGIN_FRAME_ARGS_H_
 #define CC_OUTPUT_BEGIN_FRAME_ARGS_H_
 
 #include "base/location.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;
 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
 
 /**
  * In debug builds we trace the creation origin of BeginFrameArgs objects. We
  * reuse the tracked_objects::Location system to do that.
  *
  * However, in release builds we don't want this as it doubles the size of the
  * BeginFrameArgs object. As well it adds a number of largish strings to the
  * binary. Despite the argument being unused, most compilers are unable to
  * optimise it away even when unused. Instead we use the BEGINFRAME_FROM_HERE
  * macro to prevent the data even getting referenced.
@@ skipping 58 matching lines @@
  private:
   BeginFrameArgs(base::TimeTicks frame_time,
                  base::TimeTicks deadline,
                  base::TimeDelta interval,
                  BeginFrameArgsType type);
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_BEGIN_FRAME_ARGS_H_