Make InterpolationEnvironment virutal

third_party/WebKit/Source/core/animation/CSSInterpolationType.h

Index: third_party/WebKit/Source/core/animation/CSSInterpolationType.h
diff --git a/third_party/WebKit/Source/core/animation/CSSInterpolationType.h b/third_party/WebKit/Source/core/animation/CSSInterpolationType.h
index 7e72a404bb55c747a63f9ca633ecb84e488b6c15..c2eb7df21b6cd4ef4622236c585585d50907836b 100644
--- a/third_party/WebKit/Source/core/animation/CSSInterpolationType.h
+++ b/third_party/WebKit/Source/core/animation/CSSInterpolationType.h
@@ -5,13 +5,15 @@
 #ifndef CSSInterpolationType_h
 #define CSSInterpolationType_h
 
-#include "core/animation/InterpolationEnvironment.h"
+#include "core/animation/CSSInterpolationEnvironment.h"
 #include "core/animation/InterpolationType.h"
 
 namespace blink {
 
 class CSSCustomPropertyDeclaration;
+class ComputedStyle;
 class PropertyRegistration;
+class StyleResolverState;
 
 class CSSInterpolationType : public InterpolationType {
  public:
@@ -21,7 +23,8 @@ class CSSInterpolationType : public InterpolationType {
    public:
     bool IsValid(const InterpolationEnvironment& environment,
                  const InterpolationValue& underlying) const final {
-      return IsValid(environment.GetState(), underlying);
+      return IsValid(ToCSSInterpolationEnvironment(environment).GetState(),
+                     underlying);
     }
 
    protected: