Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 222 matching lines @@
 
   Scrollbar* HorizontalScrollbar() const override {
     return scrollbar_manager_.HorizontalScrollbar();
   }
   Scrollbar* VerticalScrollbar() const override {
     return scrollbar_manager_.VerticalScrollbar();
   }
 
   PlatformChromeClient* GetChromeClient() const override;
 
+  SmoothScrollSequencer* GetSmoothScrollSequencer() const override;
+
   // For composited scrolling, we allocate an extra GraphicsLayer to hold
   // onto the scrolling content. The layer can be shifted on the GPU and
   // composited at little cost.
   // Note that this is done in CompositedLayerMapping, this function being
   // only a helper.
   GraphicsLayer* LayerForScrolling() const override;
 
   // GraphicsLayers for the scrolling components.
   //
   // Any function can return nullptr if they are not accelerated.
@@ skipping 131 matching lines @@
   bool HitTestOverflowControls(HitTestResult&, const IntPoint& local_point);
 
   bool HitTestResizerInFragments(const PaintLayerFragments&,
                                  const HitTestLocation&) const;
 
   // Returns the new offset, after scrolling, of the given rect in absolute
   // coordinates, clipped by the parent's client rect.
   LayoutRect ScrollIntoView(const LayoutRect&,
                             const ScrollAlignment& align_x,
                             const ScrollAlignment& align_y,
-                            ScrollType = kProgrammaticScroll) override;
+                            ScrollType = kProgrammaticScroll,
+                            bool is_smooth = false) override;
 
   // Returns true if scrollable area is in the FrameView's collection of
   // scrollable areas. This can only happen if we're scrollable, visible to hit
   // test, and do in fact overflow. This means that 'overflow: hidden' or
   // 'pointer-events: none' layers never get added to the FrameView's
   // collection.
   bool ScrollsOverflow() const { return scrolls_overflow_; }
 
   // Rectangle encompassing the scroll corner and resizer rect.
   IntRect ScrollCornerAndResizerRect() const final;
@@ skipping 206 matching lines @@
 
 DEFINE_TYPE_CASTS(PaintLayerScrollableArea,
                   ScrollableArea,
                   scrollableArea,
                   scrollableArea->IsPaintLayerScrollableArea(),
                   scrollableArea.IsPaintLayerScrollableArea());
 
 }  // namespace blink
 
 #endif  // LayerScrollableArea_h