scrollbar-width:thin, note disagreement on width

add scrollbar-width:thin, note disagreement on width length value vs keywords vs width at all

Author: tantek

css-scrollbars-1/Overview.bs

@@ -127,7 +127,7 @@ See related <a href="https://github.com/w3c/csswg-drafts/issues/1956">Issue 1956
 
 <pre class="propdef"> 
 Name: scrollbar-width 
-Value: auto | <<length>>
+Value: auto | thin | <<length>>
 Initial: auto
 Inherited: no
 Computed value: absolute length or the keyword auto.
@@ -143,11 +143,23 @@ Negative <<length>> values are not allowed.
 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' value.
 
-When scrollbar-width is 'auto', implementations must use the default platform scrollbar width.
+<dl for=scrollbar-width>
+
+<dt><dfn >''auto''</dfn></dt>
+<dd>implementations must use the default platform scrollbar width.</dd>
+
+<dt><dfn for=scrollbar-width>''thin''</dfn></dt>
+<dd>implementations must use either a thin scrollbar width variant on platforms that provide that option, 
+or display a scrollbar thinner than the default platform scrollbar width.</dd>
+
+</dl>
 
 Note: If scrollbar-width computes to 0, the element’s scrollbars are hidden, 
 however its scrollability is not affected.
 
+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.
+
 UAs must apply the scrollbar-width value set on the root element to the viewport.
 
 Note: Unlike 'overflow' (and overflow-*) properties,