Avoid reparsing keyframe selectors

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 365ef74c1bb730d263f758cbca87805c6e037d3b..6e5adcce37f77bdbf148bd2222b9731aed353f67 100644
--- a/Source/core/css/CSSKeyframeRule.h
+++ b/Source/core/css/CSSKeyframeRule.h
@@ -45,10 +45,11 @@ public:
     }
     ~StyleKeyframe();
 
-    String keyText() const { return m_key; }
-    void setKeyText(const String& s) { m_key = s; }
+    String keyText() const;
+    void setKeyText(const String&);
+    void setKeys(const Vector<float>&);
 
-    void getKeys(Vector<float>& keys) const   { parseKeyString(m_key, keys); }
+    const Vector<float>& keys() const { return m_keys; }
 
     const StylePropertySet* properties() const { return m_properties.get(); }
     MutableStylePropertySet* mutableProperties();
@@ -61,12 +62,11 @@ public:
 private:
     StyleKeyframe();
 
-    static void parseKeyString(const String&, Vector<float>& keys);
+    static void parseKeyString(const String&, Vector<float>&);
 
     RefPtr<StylePropertySet> m_properties;
-    // FIXME: This should be a parsed vector of floats.
-    // comma separated list of keys
-    String m_key;
+    mutable String m_keyText;
+    Vector<float> m_keys;
 };
 
 class CSSKeyframeRule : public CSSRule {