Revert of Expose scroll customization for touch to JS (behind REF).

Source/core/page/scrolling/ScrollStateCallback.cpp

-// Copyright 2015 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.
-
-#include "config.h"
-#include "core/page/scrolling/ScrollStateCallback.h"
-
-namespace blink {
-
-NativeScrollBehavior ScrollStateCallback::toNativeScrollBehavior(String nativeScrollBehavior)
-{
-    DEFINE_STATIC_LOCAL(const String, disable, ("disable-native-scroll"));
-    DEFINE_STATIC_LOCAL(const String, before, ("perform-before-native-scroll"));
-    DEFINE_STATIC_LOCAL(const String, after, ("perform-after-native-scroll"));
-
-    if (nativeScrollBehavior == disable)
-        return NativeScrollBehavior::DisableNativeScroll;
-    if (nativeScrollBehavior == before)
-        return NativeScrollBehavior::PerformBeforeNativeScroll;
-    if (nativeScrollBehavior == after)
-        return NativeScrollBehavior::PerformAfterNativeScroll;
-
-    ASSERT_NOT_REACHED();
-    return NativeScrollBehavior::DisableNativeScroll;
-}
-
-} // namespace blink