Web Animations: Remove confusing interpolation subdirectory.

Source/core/animation/interpolation/DefaultStyleInterpolation.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 DefaultStyleInterpolation_h
-#define DefaultStyleInterpolation_h
-
-#include "core/animation/interpolation/StyleInterpolation.h"
-#include "core/css/resolver/StyleBuilder.h"
-
-namespace blink {
-
-class DefaultStyleInterpolation : public StyleInterpolation {
-public:
-    static PassRefPtrWillBeRawPtr<DefaultStyleInterpolation> create(CSSValue* start, CSSValue* end, CSSPropertyID id)
-    {
-        return adoptRefWillBeNoop(new DefaultStyleInterpolation(start, end, id));
-    }
-
-    virtual void apply(StyleResolverState& state) const
-    {
-        StyleBuilder::applyProperty(m_id, state, toInterpolableBool(m_cachedValue.get())->value() ? m_endCSSValue.get() : m_startCSSValue.get());
-    }
-
-    virtual void trace(Visitor* visitor) OVERRIDE
-    {
-        StyleInterpolation::trace(visitor);
-        visitor->trace(m_startCSSValue);
-        visitor->trace(m_endCSSValue);
-    }
-
-private:
-    DefaultStyleInterpolation(CSSValue* start, CSSValue* end, CSSPropertyID id)
-        : StyleInterpolation(InterpolableBool::create(false), InterpolableBool::create(true), id)
-        , m_startCSSValue(start)
-        , m_endCSSValue(end)
-    {
-    }
-
-    RefPtrWillBeMember<CSSValue> m_startCSSValue;
-    RefPtrWillBeMember<CSSValue> m_endCSSValue;
-};
-
-}
-
-#endif