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 m_scrollbarManager.horizontalScrollbar();
   }
   Scrollbar* verticalScrollbar() const override {
     return m_scrollbarManager.verticalScrollbar();
   }
 
   HostWindow* getHostWindow() 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 122 matching lines @@
   bool hitTestOverflowControls(HitTestResult&, const IntPoint& localPoint);
 
   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& alignX,
                             const ScrollAlignment& alignY,
-                            ScrollType = ProgrammaticScroll) override;
+                            ScrollType = ProgrammaticScroll,
+                            bool isSmooth = 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 m_scrollsOverflow; }
 
   // Rectangle encompassing the scroll corner and resizer rect.
   IntRect scrollCornerAndResizerRect() const final;
@@ skipping 208 matching lines @@
 
 DEFINE_TYPE_CASTS(PaintLayerScrollableArea,
                   ScrollableArea,
                   scrollableArea,
                   scrollableArea->isPaintLayerScrollableArea(),
                   scrollableArea.isPaintLayerScrollableArea());
 
 }  // namespace blink
 
 #endif  // LayerScrollableArea_h