Revert of Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/platform/scroll/SmoothScrollSequencer.h

-// Copyright (c) 2017 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 SmoothScrollSequencer_h
-#define SmoothScrollSequencer_h
-
-#include <utility>
-#include "platform/heap/Handle.h"
-#include "platform/scroll/ScrollTypes.h"
-
-namespace blink {
-
-class ScrollableArea;
-
-// A sequencer that queues the nested scrollers from inside to outside,
-// so that they can be animated from outside to inside when smooth scroll
-// is called.
-class PLATFORM_EXPORT SmoothScrollSequencer final
-    : public GarbageCollected<SmoothScrollSequencer> {
- public:
-  SmoothScrollSequencer();
-  // Add a scroll offset animation to the back of a queue.
-  void QueueAnimation(ScrollableArea*, ScrollOffset);
-
-  // Run the animation at the back of the queue.
-  void RunQueuedAnimations();
-
-  // Abort the currently running animation and all the animations in the queue.
-  void AbortAnimations();
-
-  DECLARE_TRACE();
-
- private:
-  typedef std::pair<Member<ScrollableArea>, ScrollOffset> ScrollerAndOffsetPair;
-  HeapVector<ScrollerAndOffsetPair> queue_;
-  Member<ScrollableArea> current_scrollable_;
-};
-
-}  // namespace blink
-
-#endif  // SmoothScrollSequencer_h