[css-overflow-3] Remove border-box overflow concept per WG resolution. (Will be restored in UI 4 or Overflow 4 as needed.)

Author: fantasai

css-overflow-3/Overview.bs

@@ -249,33 +249,6 @@ Scrollable overflow</h3>
 	or is it something browsers would like to fix someday?
 
 
-<h3 id="border-box">
-Border box overflow</h3>
-
-	<p class="issue">
-		This concept has been proposed for some uses, such as for
-		determining what the 'outline' property goes around, and
-		as the basis of a coordinate system for specifying clips and masks,
-		but it's not clear if it's needed.
-
-	The <dfn>border-box overflow</dfn> of a box is the
-	union of the box's border edge and the border edges of
-	the box's descendants.
-
-	<p class="issue">
-		If needed, define more formally, as for scrollable overflow above.
-		(Maybe even share the definitions in an appropriate way!)
-
-	The <dfn>border-box overflow region</dfn> is the non-rectangular region
-	occupied by the <a>border-box overflow</a>, and the
-	<dfn>border-box overflow rectangle</dfn> is
-	the minimal rectangle whose axis is aligned to the box's axes
-	and contains the <a>border-box overflow region</a>.
-	Note that the <a>border-box overflow rectangle</a> is a rectangle
-	in the box's coordinate system, but might be non-rectangular
-	in other coordinate systems due to transforms [[CSS3-TRANSFORMS]].
-
-
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