cc: Remove AsValue virtual from DisplayItem.

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 <memory>
-#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 std::unique_ptr<ConvertableToTraceFormat> AsTraceableDisplayItemList(
-      scoped_refptr<const DisplayItemList> list,
-      bool include_items) {
-    return std::unique_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_