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 692a3816dcd465e23220f647099629765dbbe43e..5323a536a941a5fd9bca25041cd16c34fe8e8d9f 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;
@@ -227,7 +229,9 @@ 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();