Update animation when changes in animation keyframes are detected.

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 93f8466443de5b7131643b427516e30658e0beaf..db190e7a29556c5170a296c491e45a7a88fc668d 100644
--- a/Source/core/css/CSSKeyframesRule.h
+++ b/Source/core/css/CSSKeyframesRule.h
@@ -61,13 +61,17 @@ public:
 
     void traceAfterDispatch(Visitor*);
 
+    void styleChanged() { m_version++; }
+    unsigned version() const { return m_version; }
+
 private:
     StyleRuleKeyframes();
     explicit StyleRuleKeyframes(const StyleRuleKeyframes&);
 
     WillBeHeapVector<RefPtrWillBeMember<StyleRuleKeyframe> > m_keyframes;
     AtomicString m_name;
-    bool m_isPrefixed;
+    unsigned m_version : 31;
+    unsigned m_isPrefixed : 1;
 };
 
 DEFINE_STYLE_RULE_TYPE_CASTS(Keyframes);
@@ -101,6 +105,8 @@ public:
     bool isVendorPrefixed() const { return m_isPrefixed; }
     void setVendorPrefixed(bool isPrefixed) { m_isPrefixed = isPrefixed; }
 
+    void styleChanged() { m_keyframesRule->styleChanged(); }
+
     virtual void trace(Visitor*) override;
 
 private: