DataTransfer: Make |types| be a FrozenArray<DOMString>.

third_party/WebKit/Source/core/clipboard/DataTransfer.h

 /*
  * Copyright (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2001 Tobias Anton (anton@stud.fbi.fh-darmstadt.de)
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2008 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 69 matching lines @@
   bool DropEffectIsUninitialized() const {
     return drop_effect_ == "uninitialized";
   }
   String effectAllowed() const { return effect_allowed_; }
   void setEffectAllowed(const String&);
 
   void clearData(const String& type = String());
   String getData(const String& type) const;
   void setData(const String& type, const String& data);
 
-  // extensions beyond IE's API
-  Vector<String> types() const;
+  // Used by the bindings code to determine whether to call types() again.
+  bool hasDataStoreItemListChanged() const;
+
+  Vector<String> types();
   FileList* files() const;
 
   IntPoint DragLocation() const { return drag_loc_; }
   void setDragImage(Element*, int x, int y);
   void ClearDragImage();
   void SetDragImageResource(ImageResourceContent*, const IntPoint&);
   void SetDragImageElement(Node*, const IntPoint&);
 
   std::unique_ptr<DragImage> CreateDragImage(IntPoint& drag_location,
                                              LocalFrame*) const;
@@ skipping 37 matching lines @@
   bool HasStringOfType(const String&) const;
 
   // Instead of using this member directly, prefer to use the can*() methods
   // above.
   DataTransferAccessPolicy policy_;
   String drop_effect_;
   String effect_allowed_;
   DataTransferType transfer_type_;
   Member<DataObject> data_object_;
 
+  bool data_store_item_list_changed_;
+
   IntPoint drag_loc_;
   Member<ImageResourceContent> drag_image_;
   Member<Node> drag_image_element_;
 };
 
 DragOperation ConvertDropZoneOperationToDragOperation(
     const String& drag_operation);
 String ConvertDragOperationToDropZoneOperation(DragOperation);
 
 }  // namespace blink
 
 #endif  // DataTransfer_h