Have DataObject create less copies of mime type lists.

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

 /*
  * Copyright (c) 2008, 2009, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 18 matching lines @@
  */
 
 #ifndef DataObject_h
 #define DataObject_h
 
 #include "core/CoreExport.h"
 #include "core/clipboard/DataObjectItem.h"
 #include "platform/PasteMode.h"
 #include "platform/Supplementable.h"
 #include "platform/heap/Handle.h"
-#include "wtf/ListHashSet.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/Vector.h"
 #include "wtf/text/StringHash.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class KURL;
 class SharedBuffer;
 class WebDragData;
@@ skipping 16 matching lines @@
     // FIXME: Implement V8DataTransferItemList::indexedPropertyDeleter to get this called.
     void deleteItem(unsigned long index);
     void clearAll();
     // Returns null if an item already exists with the provided type.
     DataObjectItem* add(const String& data, const String& type);
     DataObjectItem* add(File*);
 
     // WebCore helpers.
     void clearData(const String& type);
 
-    ListHashSet<String> types() const;
+    Vector<String> types() const;
     String getData(const String& type) const;
     void setData(const String& type, const String& data);
 
     void urlAndTitle(String& url, String* title = 0) const;
     void setURLAndTitle(const String& url, const String& title);
     void htmlAndBaseURL(String& html, KURL& baseURL) const;
     void setHTMLAndBaseURL(const String& html, const KURL& baseURL);
 
     // Used for dragging in files from the desktop.
     bool containsFilenames() const;
@@ skipping 24 matching lines @@
     HeapVector<Member<DataObjectItem>> m_itemList;
 
     // State of Shift/Ctrl/Alt/Meta keys and Left/Right/Middle mouse buttons
     int m_modifiers;
     String m_filesystemId;
 };
 
 } // namespace blink
 
 #endif