Define overflow directions in terms of block-end and inline-end.

Fixes w3c#1569.

Author: dbaron

cssom-view-1/Overview.bs

@@ -139,24 +139,7 @@ An element <var>body</var> (which will be <a>the HTML <code>body</code> element<
 Note: A <{body}> element that is <a>potentially scrollable</a> might not have a <a>scrolling box</a>.
 For instance, it could have a used value of 'overflow' being ''overflow/auto'' but not have its content overflowing its content area.
 
-A <a>scrolling box</a> of a <a>viewport</a> or element has two <dfn>overflow directions</dfn>, depending on the <a>viewport’s</a> or
-element's <a>block flow direction</a> and <a>inline base direction</a>, as follows:
-
-<dl class=switch>
-    <dt>If the <a>block flow direction</a> is top-to-bottom and the <a>inline base direction</a> is left-to-right
-    <dt>If the <a>block flow direction</a> is left-to-right and the <a>inline base direction</a> is left-to-right
-    <dd>Rightward and downward.
-
-    <dt>If the <a>block flow direction</a> is top-to-bottom and the <a>inline base direction</a> is right-to-left
-    <dt>If the <a>block flow direction</a> is right-to-left and the <a>inline base direction</a> is left-to-right
-    <dd>Leftward and downward.
-
-    <dt>If the <a>block flow direction</a> is right-to-left and the <a>inline base direction</a> is right-to-left
-    <dd>Leftward and upward.
-
-    <dt>If the <a>block flow direction</a> is left-to-right and the <a>inline base direction</a> is right-to-left
-    <dd>Rightward and upward.
-</dl>
+A <a>scrolling box</a> of a <a>viewport</a> or element has two <dfn>overflow directions</dfn>, which are the <a>block-end</a> and <a>inline-end</a> directions for that viewport or element.
 
 The term <dfn>scrolling area</dfn> refers to a box of a <a>viewport</a> or an element that has the following edges, depending on the
 <a>viewport’s</a> or element's <a>scrolling box’s</a> <a>overflow directions</a>.