blink: Add backdrop-filter support

Source/core/animation/StringKeyframe.cpp

 // 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.
 
 #include "config.h"
 #include "core/animation/StringKeyframe.h"
 
 #include "core/animation/AngleSVGInterpolation.h"
 #include "core/animation/CSSValueInterpolationType.h"
 #include "core/animation/ColorStyleInterpolation.h"
@@ skipping 422 matching lines @@
     }
 
     case CSSPropertyStrokeDasharray: {
         RefPtrWillBeRawPtr<Interpolation> interpolation = SVGStrokeDasharrayStyleInterpolation::maybeCreate(*fromCSSValue, *toCSSValue, property);
         if (interpolation)
             return interpolation.release();
 
         break;
     }
 
-    case CSSPropertyWebkitFilter: {
+    case CSSPropertyWebkitFilter:
+    case CSSPropertyBackdropFilter: {
         RefPtrWillBeRawPtr<Interpolation> interpolation = FilterStyleInterpolation::maybeCreateList(*fromCSSValue, *toCSSValue, property);
         if (interpolation)
             return interpolation.release();
 
         // FIXME: Support drop shadow interpolation.
         return createLegacyStyleInterpolation(property, end, element, baseStyle);
         break;
     }
 
     case CSSPropertyTranslate: {
@@ skipping 146 matching lines @@
     RefPtrWillBeRawPtr<SVGPropertyBase> fromValue = attribute->currentValueBase()->cloneForAnimation(m_value);
     RefPtrWillBeRawPtr<SVGPropertyBase> toValue = attribute->currentValueBase()->cloneForAnimation(toSVGPropertySpecificKeyframe(end).value());
 
     if (!fromValue || !toValue)
         return nullptr;
 
     return createSVGInterpolation(fromValue.get(), toValue.get(), attribute.get());
 }
 
 } // namespace blink