Delete unused AnimatableValue code

third_party/WebKit/Source/core/animation/animatable/AnimatableValueKeyframe.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 AnimatableValueKeyframe_h
 #define AnimatableValueKeyframe_h
 
 #include "core/CoreExport.h"
 #include "core/animation/Keyframe.h"
 #include "core/animation/animatable/AnimatableValue.h"
@@ skipping 30 matching lines @@
         EffectModel::CompositeOperation composite) {
       return adoptRef(new PropertySpecificKeyframe(
           offset, std::move(easing), std::move(value), composite));
     }
 
     AnimatableValue* value() const { return m_value.get(); }
     PassRefPtr<AnimatableValue> getAnimatableValue() const final {
       return m_value;
     }
 
-    bool isNeutral() const final { return m_value->isNeutral(); }
+    bool isNeutral() const final { return false; }
     PassRefPtr<Keyframe::PropertySpecificKeyframe> neutralKeyframe(
         double offset,
-        PassRefPtr<TimingFunction> easing) const final;
+        PassRefPtr<TimingFunction> easing) const final {
+      NOTREACHED();
+      return nullptr;
+    }
     PassRefPtr<Interpolation> createInterpolation(
         const PropertyHandle&,
         const Keyframe::PropertySpecificKeyframe& end) const final;
 
    private:
     PropertySpecificKeyframe(double offset,
                              PassRefPtr<TimingFunction> easing,
                              PassRefPtr<AnimatableValue> value,
                              EffectModel::CompositeOperation composite)
         : Keyframe::PropertySpecificKeyframe(offset,
@@ skipping 35 matching lines @@
                   value.isAnimatableValueKeyframe());
 DEFINE_TYPE_CASTS(AnimatableValuePropertySpecificKeyframe,
                   Keyframe::PropertySpecificKeyframe,
                   value,
                   value->isAnimatableValuePropertySpecificKeyframe(),
                   value.isAnimatableValuePropertySpecificKeyframe());
 
 }  // namespace blink
 
 #endif