Implement Element.scrollIntoView for scroll-behavior: smooth.

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

Index: third_party/WebKit/Source/core/frame/RootFrameViewport.h
diff --git a/third_party/WebKit/Source/core/frame/RootFrameViewport.h b/third_party/WebKit/Source/core/frame/RootFrameViewport.h
index 2c276dad048baa7fb450eb589bb964f4bb325968..473b4d2d56ec3f9004b2e889f9d3d4c1c7ad1b88 100644
--- a/third_party/WebKit/Source/core/frame/RootFrameViewport.h
+++ b/third_party/WebKit/Source/core/frame/RootFrameViewport.h
@@ -61,6 +61,7 @@ class CORE_EXPORT RootFrameViewport final
   LayoutRect ScrollIntoView(const LayoutRect& rect_in_content,
                             const ScrollAlignment& align_x,
                             const ScrollAlignment& align_y,
+                            bool is_smooth,
                             ScrollType = kProgrammaticScroll) override;
   IntRect VisibleContentRect(
       IncludeScrollbarsInRect = kExcludeScrollbars) const override;
@@ -95,6 +96,7 @@ class CORE_EXPORT RootFrameViewport final
   ScrollResult UserScroll(ScrollGranularity, const FloatSize&) override;
   bool ScrollAnimatorEnabled() const override;
   PlatformChromeClient* GetChromeClient() const override;
+  SmoothScrollSequencer* GetSmoothScrollSequencer() const override;
   void ServiceScrollAnimations(double) override;
   void UpdateCompositorScrollAnimations() override;
   void CancelProgrammaticScrollAnimation() override;