Implement Element.scrollIntoView for scroll-behavior: smooth.

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

Index: third_party/WebKit/Source/core/frame/LocalFrameView.h
diff --git a/third_party/WebKit/Source/core/frame/LocalFrameView.h b/third_party/WebKit/Source/core/frame/LocalFrameView.h
index 56db6c0c199743ce55ab403405ac5228c6373687..ef0686c5822b413cfd701acacabc8a6e81a9c841 100644
--- a/third_party/WebKit/Source/core/frame/LocalFrameView.h
+++ b/third_party/WebKit/Source/core/frame/LocalFrameView.h
@@ -52,6 +52,7 @@
 #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"
@@ -469,6 +470,7 @@ class CORE_EXPORT LocalFrameView final
   LayoutRect ScrollIntoView(const LayoutRect& rect_in_content,
                             const ScrollAlignment& align_x,
                             const ScrollAlignment& align_y,
+                            bool is_smooth,
                             ScrollType = kProgrammaticScroll) override;
 
   // The window that hosts the LocalFrameView. The LocalFrameView will
@@ -476,6 +478,8 @@ class CORE_EXPORT LocalFrameView final
   // coordinate space.
   PlatformChromeClient* GetChromeClient() const;
 
+  SmoothScrollSequencer* GetSmoothScrollSequencer() const override;
+
   // Functions for child manipulation and inspection.
   bool IsSelfVisible() const {
     return self_visible_;