Implement Element.scrollIntoView for scroll-behavior: smooth.

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

 /*
  * Copyright (C) 2006, 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 75 matching lines @@
     // Pointer Lock
     // https://w3c.github.io/pointerlock/#extensions-to-the-element-interface
     [MeasureAs=ElementRequestPointerLock] void requestPointerLock();
 
     // CSSOM View Module
     // https://dev.w3.org/csswg/cssom-view/#extension-to-the-element-interface
     // FIXME: getClientRect() and getBoundingClientRect() should
     // 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);
     [RuntimeEnabled=CSSOMSmoothScroll] void scrollTo(unrestricted double x, unrestricted double y);
     [RuntimeEnabled=CSSOMSmoothScroll] void scrollBy(optional ScrollToOptions options);
     [RuntimeEnabled=CSSOMSmoothScroll] void scrollBy(unrestricted double x, unrestricted double y);
     attribute unrestricted double scrollTop;
     attribute unrestricted double scrollLeft;
     readonly attribute long scrollWidth;
     readonly attribute long scrollHeight;
@@ skipping 30 matching lines @@
     attribute EventHandler oncut;
     attribute EventHandler onpaste;
     attribute EventHandler onsearch;
     attribute EventHandler onselectstart;
     attribute EventHandler onwheel;
 };
 
 Element implements ParentNode;
 Element implements ChildNode;
 Element implements NonDocumentTypeChildNode;