Make InterpolationEnvironment virutal

third_party/WebKit/Source/core/animation/SVGLengthInterpolationType.cpp

 // 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.
 
 #include "core/animation/SVGLengthInterpolationType.h"
 
-#include "core/animation/InterpolationEnvironment.h"
+#include <memory>
+#include "core/animation/SVGInterpolationEnvironment.h"
 #include "core/animation/StringKeyframe.h"
 #include "core/css/CSSHelper.h"
 #include "core/svg/SVGElement.h"
 #include "core/svg/SVGLength.h"
 #include "core/svg/SVGLengthContext.h"
-#include <memory>
 
 namespace blink {
 
 std::unique_ptr<InterpolableValue>
 SVGLengthInterpolationType::NeutralInterpolableValue() {
   std::unique_ptr<InterpolableList> list_of_values =
       InterpolableList::Create(CSSPrimitiveValue::kLengthUnitTypeCount);
   for (size_t i = 0; i < CSSPrimitiveValue::kLengthUnitTypeCount; ++i)
     list_of_values->Set(i, InterpolableNumber::Create(0));
 
@@ skipping 84 matching lines @@
     const NonInterpolableValue*) const {
   NOTREACHED();
   // This function is no longer called, because apply has been overridden.
   return nullptr;
 }
 
 void SVGLengthInterpolationType::Apply(
     const InterpolableValue& interpolable_value,
     const NonInterpolableValue* non_interpolable_value,
     InterpolationEnvironment& environment) const {
-  SVGElement& element = environment.SvgElement();
+  SVGElement& element = ToSVGInterpolationEnvironment(environment).SvgElement();
   SVGLengthContext length_context(&element);
   element.SetWebAnimatedAttribute(
       Attribute(),
       ResolveInterpolableSVGLength(interpolable_value, length_context,
                                    unit_mode_, negative_values_forbidden_));
 }
 
 }  // namespace blink