Add protobuf serialization to DisplayItemList

cc/playback/display_item_list_settings.h

Index: cc/playback/display_item_list_settings.h
diff --git a/cc/playback/display_item_list_settings.h b/cc/playback/display_item_list_settings.h
index 85fe8db3fa6d53c550efebd341ed28dcc8f27afa..9c081623b8ae66958170a0953203e415d90cd5b7 100644
--- a/cc/playback/display_item_list_settings.h
+++ b/cc/playback/display_item_list_settings.h
@@ -11,11 +11,18 @@
 
 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;
 };