First programmatic smooth scroll should run on the compositor if it can

third_party/WebKit/Source/core/frame/FrameView.h

 /*
    Copyright (C) 1997 Martin Jones (mjones@kde.org)
              (C) 1998 Waldo Bastian (bastian@kde.org)
              (C) 1998, 1999 Torben Weis (weis@kde.org)
              (C) 1999 Lars Knoll (knoll@kde.org)
              (C) 1999 Antti Koivisto (koivisto@kde.org)
    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 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
@@ skipping 357 matching lines @@
     bool shouldScrollOnMainThread() const override;
     GraphicsLayer* layerForScrolling() const override;
     GraphicsLayer* layerForHorizontalScrollbar() const override;
     GraphicsLayer* layerForVerticalScrollbar() const override;
     GraphicsLayer* layerForScrollCorner() const override;
     int scrollSize(ScrollbarOrientation) const override;
     bool isScrollCornerVisible() const override;
     bool userInputScrollable(ScrollbarOrientation) const override;
     bool shouldPlaceVerticalScrollbarOnLeft() const override;
     Widget* getWidget() override;
+    CompositorAnimationTimeline* compositorAnimationTimeline() const override;
 
     LayoutRect scrollIntoView(
         const LayoutRect& rectInContent,
         const ScrollAlignment& alignX,
         const ScrollAlignment& alignY,
         ScrollType = ProgrammaticScroll) override;
 
     // The window that hosts the FrameView. The FrameView will communicate scrolls and repaints to the
     // host window in the window's coordinate space.
     HostWindow* getHostWindow() const;
@@ skipping 540 matching lines @@
     if (m_visuallyNonEmptyPixelCount > visualPixelThreshold)
         setIsVisuallyNonEmpty();
 }
 
 DEFINE_TYPE_CASTS(FrameView, Widget, widget, widget->isFrameView(), widget.isFrameView());
 DEFINE_TYPE_CASTS(FrameView, ScrollableArea, scrollableArea, scrollableArea->isFrameView(), scrollableArea.isFrameView());
 
 } // namespace blink
 
 #endif // FrameView_h