[Oilpan]: Move CSSFontSelectorClient to the oilpan heap using transition types.

Source/core/css/CSSFontSelector.h

 /*
  * Copyright (C) 2007, 2008, 2011 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 10 matching lines @@
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef CSSFontSelector_h
 #define CSSFontSelector_h
 
 #include "core/css/FontFaceCache.h"
 #include "core/fetch/ResourcePtr.h"
+#include "heap/Handle.h"
 #include "platform/Timer.h"
 #include "platform/fonts/FontSelector.h"
 #include "platform/fonts/GenericFontFamilySettings.h"
 #include "wtf/Forward.h"
 #include "wtf/HashMap.h"
 #include "wtf/HashSet.h"
 
 namespace WebCore {
 
 class CSSFontFace;
@@ skipping 55 matching lines @@
     void loadPendingFonts();
 
 private:
     explicit CSSFontSelector(Document*);
 
     void dispatchInvalidationCallbacks();
 
     Document* m_document;
     // FIXME: Move to Document or StyleEngine.
     FontFaceCache m_fontFaceCache;
-    HashSet<CSSFontSelectorClient*> m_clients;
+    WillBePersistentHeapHashSet<RawPtrWillBeWeakMember<CSSFontSelectorClient> > m_clients;
 
     FontLoader m_fontLoader;
     GenericFontFamilySettings m_genericFontFamilySettings;
 };
 
 } // namespace WebCore
 
 #endif // CSSFontSelector_h