Delete unused AnimatableValue code

third_party/WebKit/Source/core/animation/animatable/AnimatableValue.cpp

Index: third_party/WebKit/Source/core/animation/animatable/AnimatableValue.cpp
diff --git a/third_party/WebKit/Source/core/animation/animatable/AnimatableValue.cpp b/third_party/WebKit/Source/core/animation/animatable/AnimatableValue.cpp
index 34afcfcb67c83fdf7217cafd40e6ad830f3af4b2..2f6db6afe4d0b5e3e4fbba54b2ab2dc8f0f877f8 100644
--- a/third_party/WebKit/Source/core/animation/animatable/AnimatableValue.cpp
+++ b/third_party/WebKit/Source/core/animation/animatable/AnimatableValue.cpp
@@ -30,26 +30,17 @@
 
 #include "core/animation/animatable/AnimatableValue.h"
 
-#include "core/animation/animatable/AnimatableNeutral.h"
 #include "wtf/StdLibExtras.h"
 #include <algorithm>
 
 namespace blink {
 
-PassRefPtr<AnimatableValue> AnimatableValue::neutralValue() {
-  DEFINE_STATIC_REF(AnimatableNeutral, neutralSentinelValue,
-                    (AnimatableNeutral::create()));
-  return neutralSentinelValue;
-}
-
 PassRefPtr<AnimatableValue> AnimatableValue::interpolate(
     const AnimatableValue* left,
     const AnimatableValue* right,
     double fraction) {
   DCHECK(left);
   DCHECK(right);
-  DCHECK(!left->isNeutral());
-  DCHECK(!right->isNeutral());
 
   if (fraction && fraction != 1 && left->isSameType(right))
     return left->interpolateTo(right, fraction);