Oilpan: Move CSSStyleDeclaration and subclasses to the heap using transistion types.

Source/core/css/CSSKeyframeRule.h

Index: Source/core/css/CSSKeyframeRule.h
diff --git a/Source/core/css/CSSKeyframeRule.h b/Source/core/css/CSSKeyframeRule.h
index 31d78d3a845109af695226311a066b3255a71a97..c50566bd22af2220644111cc8cc7ce73fc29bae6 100644
--- a/Source/core/css/CSSKeyframeRule.h
+++ b/Source/core/css/CSSKeyframeRule.h
@@ -85,13 +85,13 @@ public:
 
     CSSStyleDeclaration* style() const;
 
-    virtual void trace(Visitor* visitor) OVERRIDE { CSSRule::trace(visitor); }
+    virtual void trace(Visitor*) OVERRIDE;
 
 private:
     CSSKeyframeRule(StyleKeyframe*, CSSKeyframesRule* parent);
 
     RefPtr<StyleKeyframe> m_keyframe;
-    mutable RefPtr<StyleRuleCSSStyleDeclaration> m_propertiesCSSOMWrapper;
+    mutable RefPtrWillBeMember<StyleRuleCSSStyleDeclaration> m_propertiesCSSOMWrapper;
 
     friend class CSSKeyframesRule;
 };