Hollow out more of the tracing system in oilpan

sky/engine/core/css/FontFace.h

Index: sky/engine/core/css/FontFace.h
diff --git a/sky/engine/core/css/FontFace.h b/sky/engine/core/css/FontFace.h
index 8072772a5701b8cfce52e0372743d82746bdb57f..9c1d32f87063c43face6055915e3fe1a3929a523 100644
--- a/sky/engine/core/css/FontFace.h
+++ b/sky/engine/core/css/FontFace.h
@@ -94,8 +94,6 @@ public:
     FontTraits traits() const;
     CSSFontFace* cssFontFace() { return m_cssFontFace.get(); }
 
-    void trace(Visitor*);
-
     bool hadBlankText() const;
 
     class LoadFontCallback : public RefCounted<LoadFontCallback> {
@@ -103,7 +101,6 @@ public:
         virtual ~LoadFontCallback() { }
         virtual void notifyLoaded(FontFace*) = 0;
         virtual void notifyError(FontFace*) = 0;
-        virtual void trace(Visitor*) { }
     };
     void loadWithCallback(PassRefPtr<LoadFontCallback>, ExecutionContext*);