Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/platform/scroll/ProgrammaticScrollAnimator.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 ProgrammaticScrollAnimator_h
 #define ProgrammaticScrollAnimator_h
 
 #include <memory>
 #include "platform/heap/Handle.h"
 #include "platform/scroll/ScrollAnimatorCompositorCoordinator.h"
@@ skipping 12 matching lines @@
   WTF_MAKE_NONCOPYABLE(ProgrammaticScrollAnimator);
 
  public:
   static ProgrammaticScrollAnimator* Create(ScrollableArea* scrollable_area) {
     return new ProgrammaticScrollAnimator(scrollable_area);
   }
 
   virtual ~ProgrammaticScrollAnimator();
 
   void ScrollToOffsetWithoutAnimation(const ScrollOffset&);
-  void AnimateToOffset(const ScrollOffset&);
+  void AnimateToOffset(const ScrollOffset&,
+                       bool sequenced_for_smooth_scroll = false);
 
   // ScrollAnimatorCompositorCoordinator implementation.
   void ResetAnimationState() override;
   void CancelAnimation() override;
   void TakeOverCompositorAnimation() override{};
   ScrollableArea* GetScrollableArea() const override {
     return scrollable_area_;
   }
   void TickAnimation(double monotonic_time) override;
   void UpdateCompositorAnimations() override;
   void NotifyCompositorAnimationFinished(int group_id) override;
   void NotifyCompositorAnimationAborted(int group_id) override{};
   void LayerForCompositedScrollingDidChange(
       CompositorAnimationTimeline*) override;
 
   DECLARE_TRACE();
 
  private:
   explicit ProgrammaticScrollAnimator(ScrollableArea*);
 
   void NotifyOffsetChanged(const ScrollOffset&);
+  void AnimationFinished();
 
   Member<ScrollableArea> scrollable_area_;
   std::unique_ptr<CompositorScrollOffsetAnimationCurve> animation_curve_;
   ScrollOffset target_offset_;
   double start_time_;
+  bool sequenced_for_smooth_scroll_;
 };
 
 }  // namespace blink
 
 #endif  // ProgrammaticScrollAnimator_h