Implement Element.scrollIntoView for scroll-behavior: smooth.

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

Index: third_party/WebKit/Source/core/dom/Element.idl
diff --git a/third_party/WebKit/Source/core/dom/Element.idl b/third_party/WebKit/Source/core/dom/Element.idl
index 07e6d7aa90489f5b14954851fb6eb6dc062b6769..cc91237af8c92fd93d9bf6ef5410db99081ea774 100644
--- a/third_party/WebKit/Source/core/dom/Element.idl
+++ b/third_party/WebKit/Source/core/dom/Element.idl
@@ -94,7 +94,7 @@ interface Element : Node {
     ClientRectList getClientRects();
     ClientRect getBoundingClientRect();
     // FIXME: scrollIntoView() should have a ScrollIntoViewOptions dictionary argument.
-    void scrollIntoView(optional boolean alignWithTop);
+    [RaisesException] void scrollIntoView(optional (ScrollIntoViewOptions or boolean)? arg);

[bokan, 2017/03/28 16:29:53]

Rather than the "or" for the argument, could we add an overload that takes
ScrollIntoViewOptions and is RuntimeEnabled? That way we don't change our public
interface without turning on the flag.

[sunyunjia, 2017/04/07 13:53:20]

Acknowledged.

     [RuntimeEnabled=CSSOMSmoothScroll, ImplementedAs=scrollTo] void scroll(optional ScrollToOptions options);
     [RuntimeEnabled=CSSOMSmoothScroll, ImplementedAs=scrollTo] void scroll(unrestricted double x, unrestricted double y);
     [RuntimeEnabled=CSSOMSmoothScroll] void scrollTo(optional ScrollToOptions options);