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

Source/core/css/CSSFontSelectorClient.h

Index: Source/core/css/CSSFontSelectorClient.h
diff --git a/Source/core/css/CSSFontSelectorClient.h b/Source/core/css/CSSFontSelectorClient.h
index 28a6c87742256f5224d530dc9d9110cf48f0a86e..6cc30f6b3f8e25f1851cdecab04c32f01a12dbdf 100644
--- a/Source/core/css/CSSFontSelectorClient.h
+++ b/Source/core/css/CSSFontSelectorClient.h
@@ -35,11 +35,13 @@ namespace WebCore {
 
 class CSSFontSelector;
 
-class CSSFontSelectorClient {
+class CSSFontSelectorClient : public NoBaseWillBeGarbageCollectedFinalized<CSSFontSelectorClient> {
 public:
     virtual ~CSSFontSelectorClient() { }
 
     virtual void fontsNeedUpdate(CSSFontSelector*) = 0;
+
+    virtual void trace(Visitor*) = 0;
 };
 
 } // namespace WebCore