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 82abd868b2ccaebaa3861518dd4589efc38f60ce..bfb2398b4c66a7e53d3ef74c6d7176d5228da776 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.h
+++ b/third_party/WebKit/Source/core/frame/FrameView.h
@@ -50,6 +50,7 @@
 #include "platform/graphics/GraphicsLayerClient.h"
 #include "platform/scroll/ScrollTypes.h"
 #include "platform/scroll/Scrollbar.h"
+#include "platform/scroll/SmoothScrollSequencer.h"
 #include "public/platform/ShapeProperties.h"
 #include "public/platform/WebDisplayMode.h"
 #include "public/platform/WebRect.h"
@@ -448,12 +449,15 @@ class CORE_EXPORT FrameView final
   LayoutRect scrollIntoView(const LayoutRect& rectInContent,
                             const ScrollAlignment& alignX,
                             const ScrollAlignment& alignY,
-                            ScrollType = ProgrammaticScroll) override;
+                            ScrollType = ProgrammaticScroll,
+                            bool isSmooth = 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.
   HostWindow* getHostWindow() const;
 
+  SmoothScrollSequencer* getSmoothScrollSequencer() const override;
+
   typedef HeapHashSet<Member<FrameViewBase>> ChildrenSet;
   typedef HeapHashSet<Member<PluginView>> PluginsSet;