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

base/trace_event/trace_event_argument.h

 // Copyright 2014 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 BASE_TRACE_EVENT_TRACE_EVENT_ARGUMENT_H_
 #define BASE_TRACE_EVENT_TRACE_EVENT_ARGUMENT_H_
 
 #include <string>
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/trace_event/trace_event.h"
 
 namespace base {
 class DictionaryValue;
 class ListValue;
 class Value;
 
-namespace debug {
+namespace trace_event {
 
 class BASE_EXPORT TracedValue : public ConvertableToTraceFormat {
  public:
   TracedValue();
 
   void EndDictionary();
   void EndArray();
 
   void SetInteger(const char* name, int value);
   void SetDouble(const char* name, double);
@@ skipping 16 matching lines @@
   ~TracedValue() override;
 
   DictionaryValue* GetCurrentDictionary();
   ListValue* GetCurrentArray();
 
   scoped_ptr<base::Value> root_;
   std::vector<Value*> stack_;
   DISALLOW_COPY_AND_ASSIGN(TracedValue);
 };
 
+}  // 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::TracedValue;
 }  // namespace debug
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_TRACE_EVENT_ARGUMENT_H_