Make IDL Callbacks non-refcounted by default

Source/core/platform/chromium/ChromiumDataObjectItem.h

 /*
  * Copyright (C) 2011 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 37 matching lines @@
 public:
     static PassRefPtr<ChromiumDataObjectItem> createFromString(const String& type, const String& data);
     static PassRefPtr<ChromiumDataObjectItem> createFromFile(PassRefPtr<File>);
     static PassRefPtr<ChromiumDataObjectItem> createFromURL(const String& url, const String& title);
     static PassRefPtr<ChromiumDataObjectItem> createFromHTML(const String& html, const KURL& baseURL);
     static PassRefPtr<ChromiumDataObjectItem> createFromSharedBuffer(const String& filename, PassRefPtr<SharedBuffer>);
     static PassRefPtr<ChromiumDataObjectItem> createFromPasteboard(const String& type, uint64_t sequenceNumber);
 
     String kind() const { return m_kind; }
     String type() const { return m_type; }
-    void getAsString(PassRefPtr<StringCallback>, ExecutionContext*) const;
+    void getAsString(PassOwnPtr<StringCallback>, ExecutionContext*) const;
     PassRefPtr<Blob> getAsFile() const;
 
     // Used to support legacy DataTransfer APIs and renderer->browser serialization.
     String internalGetAsString() const;
     PassRefPtr<SharedBuffer> sharedBuffer() const { return m_sharedBuffer; }
     String title() const { return m_title; }
     KURL baseURL() const { return m_baseURL; }
     bool isFilename() const;
 
 private:
@@ skipping 15 matching lines @@
     // Optional metadata. Currently used for URL, HTML, and dragging files in.
     String m_title;
     KURL m_baseURL;
 
     uint64_t m_sequenceNumber; // Only valid when m_source == PasteboardSource
 };
 
 } // namespace WebCore
 
 #endif // ChromiumDataObjectItem_h