[Oilpan]: Make StylePropertySet fully garbage collected.

Source/core/css/CSSKeyframeRule.cpp

 /*
  * Copyright (C) 2007, 2008, 2012 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 78 matching lines @@
     ASSERT(keys && !keys->isEmpty());
     m_keys = keys;
     m_keyText = String();
     ASSERT(m_keyText.isNull());
 }
 
 MutableStylePropertySet& StyleKeyframe::mutableProperties()
 {
     if (!m_properties->isMutable())
         m_properties = m_properties->mutableCopy();
-    return *toMutableStylePropertySet(m_properties);
+    return *toMutableStylePropertySet(m_properties.get());
 }
 
-void StyleKeyframe::setProperties(PassRefPtr<StylePropertySet> properties)
+void StyleKeyframe::setProperties(PassRefPtrWillBeRawPtr<StylePropertySet> properties)
 {
     ASSERT(properties);
     m_properties = properties;
 }
 
 String StyleKeyframe::cssText() const
 {
     StringBuilder result;
     result.append(keyText());
     result.appendLiteral(" { ");
@@ skipping 16 matching lines @@
             // "If a keyframe selector specifies negative percentage values
             // or values higher than 100%, then the keyframe will be ignored."
             keyVector->clear();
             break;
         }
         keyVector->at(i) = key / 100;
     }
     return keyVector.release();
 }
 
+void StyleKeyframe::trace(Visitor* visitor)
+{
+    visitor->trace(m_properties);
+}
 
 CSSKeyframeRule::CSSKeyframeRule(StyleKeyframe* keyframe, CSSKeyframesRule* parent)
     : CSSRule(0)
     , m_keyframe(keyframe)
 {
     setParentRule(parent);
 }
 
 CSSKeyframeRule::~CSSKeyframeRule()
 {
@@ skipping 17 matching lines @@
 }
 
 void CSSKeyframeRule::trace(Visitor* visitor)
 {
     visitor->trace(m_keyframe);
     visitor->trace(m_propertiesCSSOMWrapper);
     CSSRule::trace(visitor);
 }
 
 } // namespace WebCore