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

cc/debug/traced_value.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_DEBUG_TRACED_VALUE_H_
 #define CC_DEBUG_TRACED_VALUE_H_
 
 namespace base {
+namespace trace_event {
+class TracedValue;
+}
+
 namespace debug {
-class TracedValue;
+using ::base::trace_event::TracedValue;
 }
 }
 
 namespace cc {
 
 class TracedValue {
  public:
   static void AppendIDRef(const void* id, base::debug::TracedValue* array);
   static void SetIDRef(const void* id,
                        base::debug::TracedValue* dict,
@@ skipping 10 matching lines @@
       const char* category,
       base::debug::TracedValue* dict,
       const char* object_base_type_name,
       const char* object_name,
       const void* id);
 };
 
 }  // namespace cc
 
 #endif  // CC_DEBUG_TRACED_VALUE_H_