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 4e02a9918331fa31af5caa34ed10c06e752c7849..f5c2cae37aa4fa18b639168ba485129ada00f024 100644
--- a/third_party/WebKit/Source/core/dom/Element.h
+++ b/third_party/WebKit/Source/core/dom/Element.h
@@ -65,6 +65,8 @@ class ElementIntersectionObserverData;
 class PseudoElement;
 class ResizeObservation;
 class ResizeObserver;
+class ScrollIntoViewOptions;
+class ScrollIntoViewOptionsOrBoolean;
 class ScrollState;
 class ScrollStateCallback;
 class ScrollToOptions;
@@ -217,7 +219,10 @@ class CORE_EXPORT Element : public ContainerNode {
   // attributes.
   AttributeCollection attributesWithoutUpdate() const;
 
+  void scrollIntoView(ExceptionState&);
+  void scrollIntoView(ScrollIntoViewOptionsOrBoolean, ExceptionState&);
   void scrollIntoView(bool alignToTop = true);
+  void scrollIntoViewWithOptions(const ScrollIntoViewOptions&);
   void scrollIntoViewIfNeeded(bool centerIfNeeded = true);
 
   int offsetLeft();