Update animation when changes in animation keyframes are detected.

Source/core/css/KeyframeStyleRuleCSSStyleDeclaration.h

Index: Source/core/css/KeyframeStyleRuleCSSStyleDeclaration.h
diff --git a/Source/core/css/KeyframeStyleRuleCSSStyleDeclaration.h b/Source/core/css/KeyframeStyleRuleCSSStyleDeclaration.h
new file mode 100644
index 0000000000000000000000000000000000000000..1b0e368cf9c6f85ac925b3587e9eff64be01952b
--- /dev/null
+++ b/Source/core/css/KeyframeStyleRuleCSSStyleDeclaration.h
@@ -0,0 +1,27 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef KeyframeStyleRuleCSSStyleDeclaration_h
+#define KeyframeStyleRuleCSSStyleDeclaration_h
+
+#include "core/css/PropertySetCSSStyleDeclaration.h"
+
+namespace blink {
+
+class KeyframeStyleRuleCSSStyleDeclaration final : public StyleRuleCSSStyleDeclaration {
+public:
+    static PassRefPtrWillBeRawPtr<KeyframeStyleRuleCSSStyleDeclaration> create(MutableStylePropertySet& propertySet, CSSKeyframeRule* parentRule)
+    {
+        return adoptRefWillBeNoop(new KeyframeStyleRuleCSSStyleDeclaration(propertySet, parentRule));
+    }
+
+private:
+    KeyframeStyleRuleCSSStyleDeclaration(MutableStylePropertySet&, CSSKeyframeRule*);
+
+    virtual void didMutate(MutationType) override;
+};
+
+} // namespace blink
+
+#endif