Implement Element.scrollIntoView for scroll-behavior: smooth.

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

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2012 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 256 matching lines @@
   // PaintInvalidationState::paintingLayer() instead.
   PaintLayer* paintingLayer() const;
 
   // Scrolling is a LayoutBox concept, however some code just cares about
   // recursively scrolling our enclosing ScrollableArea(s).
   bool scrollRectToVisible(
       const LayoutRect&,
       const ScrollAlignment& alignX = ScrollAlignment::alignCenterIfNeeded,
       const ScrollAlignment& alignY = ScrollAlignment::alignCenterIfNeeded,
       ScrollType = ProgrammaticScroll,
-      bool makeVisibleInVisualViewport = true);
+      bool makeVisibleInVisualViewport = true,
+      ScrollBehavior = ScrollBehaviorAuto);
 
   // Convenience function for getting to the nearest enclosing box of a
   // LayoutObject.
   LayoutBox* enclosingBox() const;
   LayoutBoxModelObject* enclosingBoxModelObject() const;
 
   LayoutBox* enclosingScrollableBox() const;
 
   // Function to return our enclosing flow thread if we are contained inside
   // one. This function follows the containing block chain.
@@ skipping 2486 matching lines @@
 CORE_EXPORT void showLineTree(const blink::LayoutObject*);
 CORE_EXPORT void showLayoutTree(const blink::LayoutObject* object1);
 // We don't make object2 an optional parameter so that showLayoutTree
 // can be called from gdb easily.
 CORE_EXPORT void showLayoutTree(const blink::LayoutObject* object1,
                                 const blink::LayoutObject* object2);
 
 #endif
 
 #endif  // LayoutObject_h