Implement Element.scrollIntoView for scroll-behavior: smooth.

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

Index: third_party/WebKit/Source/core/frame/FrameView.h
diff --git a/third_party/WebKit/Source/core/frame/FrameView.h b/third_party/WebKit/Source/core/frame/FrameView.h
index 92309bd55b61fff3d25281fc6f741cb7d41d4331..67a81824260cd49e72c60b60ef6b9efd0a7985f9 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.h
+++ b/third_party/WebKit/Source/core/frame/FrameView.h
@@ -53,6 +53,7 @@
 #include "platform/graphics/GraphicsLayerClient.h"
 #include "platform/scroll/ScrollTypes.h"
 #include "platform/scroll/Scrollbar.h"
+#include "platform/scroll/SmoothScrollSequencer.h"
 #include "platform/wtf/Allocator.h"
 #include "platform/wtf/AutoReset.h"
 #include "platform/wtf/Forward.h"
@@ -476,12 +477,15 @@ class CORE_EXPORT FrameView final
   LayoutRect ScrollIntoView(const LayoutRect& rect_in_content,
                             const ScrollAlignment& align_x,
                             const ScrollAlignment& align_y,
-                            ScrollType = kProgrammaticScroll) override;
+                            ScrollType = kProgrammaticScroll,
+                            bool is_smooth = false) override;
 
   // The window that hosts the FrameView. The FrameView will communicate scrolls
   // and repaints to the host window in the window's coordinate space.
   PlatformChromeClient* GetChromeClient() const;
 
+  SmoothScrollSequencer* GetSmoothScrollSequencer() const override;
+
   typedef HeapHashSet<Member<FrameViewBase>> ChildrenSet;
   typedef HeapHashSet<Member<PluginView>> PluginsSet;
   typedef HeapHashSet<Member<Scrollbar>> ScrollbarsSet;