Add protobuf serialization to DisplayItemList

cc/playback/display_item_list_settings.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_PLAYBACK_DISPLAY_ITEM_LIST_SETTINGS_H_
 #define CC_PLAYBACK_DISPLAY_ITEM_LIST_SETTINGS_H_
 
 #include <cstddef>
 
 #include "cc/base/cc_export.h"
 
 namespace cc {
 
+namespace proto {
+class DisplayItemListSettings;
+}
+
 class CC_EXPORT DisplayItemListSettings {
  public:
   DisplayItemListSettings();
+  explicit DisplayItemListSettings(const proto::DisplayItemListSettings& proto);
   ~DisplayItemListSettings();
 
+  void ToProtobuf(proto::DisplayItemListSettings* proto) const;
+
   // If set, a picture will be cached inside the DisplayItemList.
   bool use_cached_picture;
 };
 
 }  // namespace cc
 
 #endif  // CC_PLAYBACK_DISPLAY_ITEM_LIST_SETTINGS_H_