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 47867a1e87d24b59fa69f1a172a5b69207cb357f..b9ea6a7b0216a7ce61fb7d8c2206a81a998c7ee5 100644
--- a/third_party/WebKit/Source/core/dom/Element.idl
+++ b/third_party/WebKit/Source/core/dom/Element.idl
@@ -93,8 +93,8 @@ interface Element : Node {
     // return DOMRectList and DOMRect respectively.
     ClientRectList getClientRects();
     ClientRect getBoundingClientRect();
-    // FIXME: scrollIntoView() should have a ScrollIntoViewOptions dictionary argument.
-    void scrollIntoView(optional boolean alignWithTop);
+
+    void scrollIntoView(optional (ScrollIntoViewOptions or boolean)? arg);

[foolip, 2017/06/14 11:51:46]

This does not match the IDL in
https://drafts.csswg.org/cssom-view/#extension-to-the-element-interface and
unfortunately there can be differences in cases like this, see
https://github.com/heycam/webidl/issues/351

Can you either have the spec changed or match the spec, and make sure that both
scrollIntoView(undefined) and scrollIntoView(null) are tested?

     [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);