Web Animations: Enable additive animations in experimental

Source/core/animation/EffectInput.h

 // Copyright 2014 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 EffectInput_h
 #define EffectInput_h
 
 #include "core/CoreExport.h"
 #include "core/animation/EffectModel.h"
 #include "wtf/Allocator.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class EffectModel;
-class EffectModelOrDictionarySequence;
+class EffectModelOrDictionarySequenceOrDictionary;
 class Dictionary;
 class Element;
 class ExceptionState;
 
 class CORE_EXPORT EffectInput {
     STATIC_ONLY(EffectInput);
 public:
     static EffectModel* convert(Element*, const Vector<Dictionary>& keyframeDictionaryVector, ExceptionState&);
-    static EffectModel* convert(Element*, const EffectModelOrDictionarySequence&, ExceptionState&);
+    static EffectModel* convert(Element*, const EffectModelOrDictionarySequenceOrDictionary&, ExceptionState&);
 };
 
 } // namespace blink
 
 #endif