[css-overflow-3] Spec Blink's behavior for abspos, because using the border box is hostile, and if Blink can do it it's presumably Web-compatible enough. Leave an issue in case anyone wants to litigate.

Author: fantasai

css-overflow-3/Overview.bs

@@ -152,14 +152,10 @@ Scrollable overflow</h3>
 		<li>the box’s own content and padding areas
 		<li>all line boxes directly contained by the box
 		<li>the margin boxes <em>unioned with</em> the border boxes
-		    of all in-flow and floated boxes
-		    for which it is the containing block
+		    of all boxes for which it is the containing block
 		    (accounting for transforms as described below).
-		<li>the padding boxes of all absolutely-positioned boxes
-		    for which it is the containing block
-		    (accounting for transforms as described below).
-
-		    Issue: Blink (and presumably WebKit) use the margin box here. Is that better?
+		    Issue: Only Blink (and presumably WebKit) use the margin box for abspos; other browsers use the border box.
+		    Can we convince everyone else to change? Because using the border box is kindof hostile.
 		<!-- testcase: http://software.hixie.ch/utilities/js/live-dom-viewer/?%3C!DOCTYPE%20html%3E%0A%3Cstyle%3E%0A%20%20div%20%7B%20height%3A%2050px%3B%20overflow%3A%20scroll%3B%20border%3A%20solid%3B%20position%3A%20relative%3B%7D%0A%20%20p%20%7B%20margin%3A%2025px%3B%20background%3A%20red%3B%20%7D%0A%20%20q%20%7B%20position%3A%20absolute%3B%20background%3A%20blue%3B%20top%3A%2025px%3B%20margin%3A%2025px%3B%20%7D%0A%3C%2Fstyle%3E%0A%3Cdiv%3E%0A%20%20%3Cp%3ETest%20%3Cq%3ETest2%0A%3C%2Fdiv%3E -->
 
 		<li>the <a>scrollable overflow regions</a> of all of the above boxes