Animation: FilterStyleInterpolation for animating filter

Source/core/animation/FilterStyleInterpolation.h

Index: Source/core/animation/FilterStyleInterpolation.h
diff --git a/Source/core/animation/FilterStyleInterpolation.h b/Source/core/animation/FilterStyleInterpolation.h
new file mode 100644
index 0000000000000000000000000000000000000000..f1c322be90557781219ecdf45803a7d1a145f357
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+++ b/Source/core/animation/FilterStyleInterpolation.h
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+// 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 FilterStyleInterpolation_h
+#define FilterStyleInterpolation_h
+
+#include "core/animation/StyleInterpolation.h"
+#include "core/css/CSSFunctionValue.h"
+
+namespace blink {
+
+class FilterStyleInterpolation : public StyleInterpolation {
+public:
+    typedef CSSValueID NonInterpolableType;
+
+    static PassRefPtrWillBeRawPtr<StyleInterpolation> maybeCreate(const CSSValue& start, const CSSValue& end, CSSPropertyID);
+
+    // The following are called by ListStyleInterpolation.
+    static bool canCreateFrom(const CSSValue& start, const CSSValue& end);
+    static PassOwnPtrWillBeRawPtr<InterpolableValue> toInterpolableValue(const CSSValue&, CSSValueID&);
+    static PassRefPtrWillBeRawPtr<CSSFunctionValue> fromInterpolableValue(const InterpolableValue&, CSSValueID, InterpolationRange = RangeAll);
+
+private:
+    FilterStyleInterpolation(PassOwnPtrWillBeRawPtr<InterpolableValue> start, PassOwnPtrWillBeRawPtr<InterpolableValue> end, CSSPropertyID id)
+        : StyleInterpolation(start, end, id)
+    {
+    }
+
+    friend class FilterStyleInterpolationTest;
+};
+
+} // namespace blink
+
+#endif // FilterStyleInterpolation_h