Introduce DEFINE_ANIMATABLE_VALUE_TYPE_CASTS to replace manual toFoo() for animatable value

Source/core/animation/AnimatableColor.h

Index: Source/core/animation/AnimatableColor.h
diff --git a/Source/core/animation/AnimatableColor.h b/Source/core/animation/AnimatableColor.h
index 51f5264c203bf4fa78b904d26d151def2abe4b65..79695106ee764ad2c36e79b45aadf1e91110cf21 100644
--- a/Source/core/animation/AnimatableColor.h
+++ b/Source/core/animation/AnimatableColor.h
@@ -78,11 +78,7 @@ private:
     const AnimatableColorImpl m_visitedLinkColor;
 };
 
-inline const AnimatableColor* toAnimatableColor(const AnimatableValue* value)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(value && value->isColor());
-    return static_cast<const AnimatableColor*>(value);
-}
+DEFINE_ANIMATABLE_VALUE_TYPE_CASTS(AnimatableColor, isColor());
 
 } // namespace WebCore