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

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

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 176 matching lines @@
     bool userInputScrollable(ScrollbarOrientation) const override { return true; }
     bool shouldPlaceVerticalScrollbarOnLeft() const override { return false; }
     bool scrollAnimatorEnabled() const override;
     void scrollControlWasSetNeedsPaintInvalidation() override { }
     void setScrollOffset(const DoublePoint&, ScrollType) override;
     GraphicsLayer* layerForContainer() const override;
     GraphicsLayer* layerForScrolling() const override;
     GraphicsLayer* layerForHorizontalScrollbar() const override;
     GraphicsLayer* layerForVerticalScrollbar() const override;
     Widget* getWidget() override;
+    CompositorAnimationTimeline* compositorAnimationTimeline() const override;
 
     // Used for gathering data on user pinch-zoom statistics.
     void userDidChangeScale();
     void sendUMAMetrics();
     void startTrackingPinchStats();
 
     // Heuristic-based function for determining if we should disable workarounds
     // for viewing websites that are not optimized for mobile devices.
     bool shouldDisableDesktopWorkarounds() const;
 
@@ skipping 34 matching lines @@
     float m_scale;
     IntSize m_size;
     float m_topControlsAdjustment;
     float m_maxPageScale;
     bool m_trackPinchZoomStatsForPage;
 };
 
 } // namespace blink
 
 #endif // VisualViewport_h