Add a counter for CSSKeyframesRule's anonymous indexed getter

Source/core/css/CSSKeyframesRule.h

Index: Source/core/css/CSSKeyframesRule.h
diff --git a/Source/core/css/CSSKeyframesRule.h b/Source/core/css/CSSKeyframesRule.h
index ac7a2107f011da4d11443138fbfb6428d3c22962..f8d505690f3e4f769cae55a64a8c590c7c91df63 100644
--- a/Source/core/css/CSSKeyframesRule.h
+++ b/Source/core/css/CSSKeyframesRule.h
@@ -101,6 +101,7 @@ public:
     // For IndexedGetter and CSSRuleList.
     unsigned length() const;
     CSSKeyframeRule* item(unsigned index) const;
+    CSSKeyframeRule* anonymousIndexedGetter(unsigned index) const;
 
     bool isVendorPrefixed() const { return m_isPrefixed; }
     void setVendorPrefixed(bool isPrefixed) { m_isPrefixed = isPrefixed; }