Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/core/layout/LayoutBox.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2006, 2007 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 570 matching lines @@
 
   void ScrollToPosition(const FloatPoint&,
                         ScrollBehavior = kScrollBehaviorInstant);
   void ScrollByRecursively(const ScrollOffset& delta);
   // If makeVisibleInVisualViewport is set, the visual viewport will be scrolled
   // if required to make the rect visible.
   void ScrollRectToVisible(const LayoutRect&,
                            const ScrollAlignment& align_x,
                            const ScrollAlignment& align_y,
                            ScrollType = kProgrammaticScroll,
-                           bool make_visible_in_visual_viewport = true);
+                           bool make_visible_in_visual_viewport = true,
+                           ScrollBehavior = kScrollBehaviorAuto);
 
   LayoutRectOutsets MarginBoxOutsets() const override {
     return margin_box_outsets_;
   }
   LayoutUnit MarginTop() const override { return margin_box_outsets_.Top(); }
   LayoutUnit MarginBottom() const override {
     return margin_box_outsets_.Bottom();
   }
   LayoutUnit MarginLeft() const override { return margin_box_outsets_.Left(); }
   LayoutUnit MarginRight() const override {
@@ skipping 1131 matching lines @@
          break_value == EBreakBetween::kLeft ||
          break_value == EBreakBetween::kPage ||
          break_value == EBreakBetween::kRecto ||
          break_value == EBreakBetween::kRight ||
          break_value == EBreakBetween::kVerso;
 }
 
 }  // namespace blink
 
 #endif  // LayoutBox_h