Implement animation tainted custom property values

third_party/WebKit/Source/core/css/KeyframeStyleRuleCSSStyleDeclaration.h

 // 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 CSSKeyframeRule;
 
 class KeyframeStyleRuleCSSStyleDeclaration final
     : public StyleRuleCSSStyleDeclaration {
  public:
   static KeyframeStyleRuleCSSStyleDeclaration* create(
       MutableStylePropertySet& propertySet,
       CSSKeyframeRule* parentRule) {
     return new KeyframeStyleRuleCSSStyleDeclaration(propertySet, parentRule);
   }
 
  private:
   KeyframeStyleRuleCSSStyleDeclaration(MutableStylePropertySet&,
                                        CSSKeyframeRule*);
 
   void didMutate(MutationType) override;
+  bool isKeyframeStyle() const final { return true; }
 };
 
 }  // namespace blink
 
 #endif