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

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

-// 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.
-
-#include "platform/scroll/SmoothScrollSequencer.h"
-
-#include "platform/scroll/ProgrammaticScrollAnimator.h"
-#include "platform/scroll/ScrollableArea.h"
-
-namespace blink {
-
-SmoothScrollSequencer::SmoothScrollSequencer() {}
-
-void SmoothScrollSequencer::QueueAnimation(ScrollableArea* scrollable,
-                                           ScrollOffset offset) {
-  ScrollerAndOffsetPair scroller_offset(scrollable, offset);
-  queue_.push_back(scroller_offset);
-}
-
-void SmoothScrollSequencer::RunQueuedAnimations() {
-  if (queue_.IsEmpty()) {
-    current_scrollable_ = nullptr;
-    return;
-  }
-  ScrollerAndOffsetPair scroller_offset = queue_.back();
-  queue_.pop_back();
-  ScrollableArea* scrollable = scroller_offset.first;
-  current_scrollable_ = scrollable;
-  ScrollOffset offset = scroller_offset.second;
-  scrollable->SetScrollOffset(offset, kProgrammaticScroll,
-                              kScrollBehaviorSmooth);
-}
-
-void SmoothScrollSequencer::AbortAnimations() {
-  if (current_scrollable_) {
-    current_scrollable_->GetProgrammaticScrollAnimator().CancelAnimation();
-    current_scrollable_ = nullptr;
-  }
-  queue_.clear();
-}
-
-DEFINE_TRACE(SmoothScrollSequencer) {
-  visitor->Trace(queue_);
-  visitor->Trace(current_scrollable_);
-}
-
-}  // namespace blink