Change various helper classes to transition types to get CSSValue entirely onto the gc heap.

Source/core/css/FontFace.h

Index: Source/core/css/FontFace.h
diff --git a/Source/core/css/FontFace.h b/Source/core/css/FontFace.h
index a33688e776053522e650d97494f395c0102f1b84..6f7c5914ad028c18338e3c1e6129ed890a09aab3 100644
--- a/Source/core/css/FontFace.h
+++ b/Source/core/css/FontFace.h
@@ -49,7 +49,8 @@ class FontFaceReadyPromiseResolver;
 class StylePropertySet;
 class StyleRuleFontFace;
 
-class FontFace : public RefCounted<FontFace> {
+class FontFace : public RefCountedWillBeRefCountedGarbageCollected<FontFace> {
+    DECLARE_GC_INFO;
 public:
     enum LoadStatus { Unloaded, Loading, Loaded, Error };
 
@@ -85,6 +86,8 @@ public:
     unsigned traitsMask() const;
     CSSFontFace* cssFontFace() { return m_cssFontFace.get(); }
 
+    void trace(Visitor*);
+
 private:
     FontFace(PassRefPtrWillBeRawPtr<CSSValue> source);
 
@@ -96,13 +99,13 @@ private:
     void resolveReadyPromises();
 
     AtomicString m_family;
-    RefPtr<CSSValue> m_src;
-    RefPtr<CSSValue> m_style;
-    RefPtr<CSSValue> m_weight;
-    RefPtr<CSSValue> m_stretch;
-    RefPtr<CSSValue> m_unicodeRange;
-    RefPtr<CSSValue> m_variant;
-    RefPtr<CSSValue> m_featureSettings;
+    RefPtrWillBeMember<CSSValue> m_src;
+    RefPtrWillBeMember<CSSValue> m_style;
+    RefPtrWillBeMember<CSSValue> m_weight;
+    RefPtrWillBeMember<CSSValue> m_stretch;
+    RefPtrWillBeMember<CSSValue> m_unicodeRange;
+    RefPtrWillBeMember<CSSValue> m_variant;
+    RefPtrWillBeMember<CSSValue> m_featureSettings;
     LoadStatus m_status;
 
     Vector<OwnPtr<FontFaceReadyPromiseResolver> > m_readyResolvers;