Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/core/dom/Element.h

Index: third_party/WebKit/Source/core/dom/Element.h
diff --git a/third_party/WebKit/Source/core/dom/Element.h b/third_party/WebKit/Source/core/dom/Element.h
index f829eee16392cb2df81517e561088a9e2ceed4d8..1f9dc5e74b8d757258427eba0aac445b7470a84e 100644
--- a/third_party/WebKit/Source/core/dom/Element.h
+++ b/third_party/WebKit/Source/core/dom/Element.h
@@ -65,6 +65,8 @@ class PseudoElement;
 class PseudoStyleRequest;
 class ResizeObservation;
 class ResizeObserver;
+class ScrollIntoViewOptions;
+class ScrollIntoViewOptionsOrBoolean;
 class ScrollState;
 class ScrollStateCallback;
 class ScrollToOptions;
@@ -217,7 +219,9 @@ class CORE_EXPORT Element : public ContainerNode {
   // attributes.
   AttributeCollection attributesWithoutUpdate() const;
 
+  void scrollIntoView(ScrollIntoViewOptionsOrBoolean);
   void scrollIntoView(bool alignToTop = true);
+  void scrollIntoViewWithOptions(const ScrollIntoViewOptions&);
   void scrollIntoViewIfNeeded(bool centerIfNeeded = true);
 
   int offsetLeft();