rm scrollbar-width length w3c#1958

removed length units from scrollbar-width per discussions in issue w3c#1958, lack of implementer interest, and at least some implementer objection to length units.

Author: tantek

css-scrollbars-1/Overview.bs

@@ -155,7 +155,7 @@ See related <a href="https://github.com/w3c/csswg-drafts/issues/1956">Issue 1956
 
 <pre class="propdef"> 
 Name: scrollbar-width 
-Value: auto | thin | none | <<length>>
+Value: auto | thin | none
 Initial: auto
 Inherited: no
 Computed value: specified keyword or absolute length
@@ -182,18 +182,8 @@ In that case, implementations may treat this value as auto.
 <dt><dfn>none</dfn></dt>
 <dd>implementations must not display any scrollbar, however the element's scrollability is not affected.
 </dd>
-<dt><dfn><<length>></dfn></dt>
-<dd>When a user agent displays one or more scrollbars for an element, 
-the thickness of those scrollbars must be no more than the computed 'scrollbar-width' length value.
-Negative <<length>> values are not allowed. If scrollbar-width computes to 0, the element’s scrollbars are hidden, 
-however its scrollability is not affected.
-</dd>
 </dl>
 
-Note: There is working group disagreement about whether to allow length values, 
-or only have keywords (auto, thin, none), or drop the scrollbar-width property altogether.
-(<a href="https://github.com/w3c/csswg-drafts/issues/1958">Issue 1958</a>)
-
 UAs must apply the scrollbar-width value set on the root element to the viewport.
 
 Note: Unlike 'overflow' (and overflow-*) properties,