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 732a418bc8b010999b9489897b639eb9c439ef16..18e00575cc3edbc2014d358d16b8cb41a0c530b2 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;
@@ -221,7 +223,9 @@ class CORE_EXPORT Element : public ContainerNode {
   // attributes.
   AttributeCollection AttributesWithoutUpdate() const;
 
+  void scrollIntoView(ScrollIntoViewOptionsOrBoolean);
   void scrollIntoView(bool align_to_top = true);
+  void scrollIntoViewWithOptions(const ScrollIntoViewOptions&);
   void scrollIntoViewIfNeeded(bool center_if_needed = true);
 
   int OffsetLeft();