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 c42da6da4c02c962aba91942f1b44f3b936c9b59..2f2f5c9ac87d8eb23afbb6c630aac075f56deee1 100644
--- a/third_party/WebKit/Source/core/frame/LocalFrameView.h
+++ b/third_party/WebKit/Source/core/frame/LocalFrameView.h
@@ -51,6 +51,7 @@
 #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"
@@ -468,6 +469,7 @@ 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
@@ -475,6 +477,8 @@ 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_;