tracing: Make ConvertableToTraceFormat move-only scoped_ptr

cc/debug/traced_display_item_list.h

 // Copyright 2015 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_DISPLAY_ITEM_LIST_H_
 #define CC_DEBUG_TRACED_DISPLAY_ITEM_LIST_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/debug/traced_value.h"
 
 namespace cc {
 
 class DisplayItemList;
 
 class TracedDisplayItemList
     : public base::trace_event::ConvertableToTraceFormat {
  public:
-  static scoped_refptr<ConvertableToTraceFormat> AsTraceableDisplayItemList(
+  static scoped_ptr<ConvertableToTraceFormat> AsTraceableDisplayItemList(
       scoped_refptr<const DisplayItemList> list,
       bool include_items) {
-    return scoped_refptr<ConvertableToTraceFormat>(
+    return scoped_ptr<ConvertableToTraceFormat>(
         new TracedDisplayItemList(list, include_items));
   }
   void AppendAsTraceFormat(std::string* out) const override;
 
  private:
   explicit TracedDisplayItemList(scoped_refptr<const DisplayItemList> list,
                                  bool include_items);
   ~TracedDisplayItemList() override;
 
   scoped_refptr<const DisplayItemList> display_item_list_;
   bool include_items_;
 
   DISALLOW_COPY_AND_ASSIGN(TracedDisplayItemList);
 };
 
 }  // namespace cc
 
 #endif  // CC_DEBUG_TRACED_DISPLAY_ITEM_LIST_H_