Support keywords in LengthStyleInterpolation

Source/core/animation/LengthStyleInterpolation.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 LengthStyleInterpolation_h
 #define LengthStyleInterpolation_h
 
 #include "core/animation/StyleInterpolation.h"
 #include "core/css/CSSPrimitiveValue.h"
 #include "platform/Length.h"
 
 namespace blink {
 
 class LengthStyleInterpolation : public StyleInterpolation {
 public:
 
     typedef void NonInterpolableType;
 
     static PassRefPtrWillBeRawPtr<LengthStyleInterpolation> create(const CSSValue& start, const CSSValue& end, CSSPropertyID id, InterpolationRange range)
     {
-        return adoptRefWillBeNoop(new LengthStyleInterpolation(toInterpolableValue(start), toInterpolableValue(end), id, range));
+        return adoptRefWillBeNoop(new LengthStyleInterpolation(toInterpolableValue(start, id), toInterpolableValue(end, id), id, range));
     }
 
-    static bool canCreateFrom(const CSSValue&);
+    static bool canCreateFrom(const CSSValue&, CSSPropertyID = CSSPropertyInvalid);
 
     virtual void apply(StyleResolverState&) const override;
 
     DECLARE_VIRTUAL_TRACE();
 
-    static PassOwnPtrWillBeRawPtr<InterpolableValue> toInterpolableValue(const CSSValue&);
+    static PassOwnPtrWillBeRawPtr<InterpolableValue> toInterpolableValue(const CSSValue&, CSSPropertyID = CSSPropertyInvalid);
     static PassRefPtrWillBeRawPtr<CSSPrimitiveValue> fromInterpolableValue(const InterpolableValue&, InterpolationRange);
 
 private:
     LengthStyleInterpolation(PassOwnPtrWillBeRawPtr<InterpolableValue> start, PassOwnPtrWillBeRawPtr<InterpolableValue> end, CSSPropertyID id,  InterpolationRange range)
         : StyleInterpolation(start, end, id)
         , m_range(range)
         { }
 
     InterpolationRange m_range;
 };
 
 }
 
 #endif