[css-flexbox] Clarify that abspos positioning is done after doing layout in flexbox.

Author: tabatkins

css-flexbox/Overview.html

@@ -706,8 +706,10 @@ <h3 class="heading settled heading" data-level=4.1 id=abspos-items><span class=s
 <p>	An absolutely-positioned child element of a <a href=#flex-container>flex container</a> does not participate in flex layout
 	beyond the <a href=#algo-flex-order>reordering step</a>.
 
-<p>	Its static position is calculated as if it did participate in flex layout,
-	but were the sole <a href=#flex-item>flex item</a> in the <a href=#flex-container>flex container</a>.
+<p>	Its static position is calculated by first doing full flex layout without the absolutely-positioned elements,
+	then positioning each absolutely-positioned child as if it were the sole <a href=#flex-item>flex item</a>
+	in the <a href=#flex-container>flex container</a>,
+	assuming it was a fixed size box of its used size.
 
 <p>	For example, by default, the static position of absolutely positioned elements is in the main-start/column-start corner,
 	corresponding to the default values of <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css-align-3/#justify-self title=justify-self>justify-self</a> and <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css-align-3/#align-self title=align-self>align-self</a>.

css-flexbox/Overview.src.html

@@ -618,8 +618,10 @@ <h3 id='abspos-items'>
 	An absolutely-positioned child element of a <i>flex container</i> does not participate in flex layout
 	beyond the <a href="#algo-flex-order">reordering step</a>.
 
-	Its static position is calculated as if it did participate in flex layout,
-	but were the sole <a>flex item</a> in the <a>flex container</a>.
+	Its static position is calculated by first doing full flex layout without the absolutely-positioned elements,
+	then positioning each absolutely-positioned child as if it were the sole <a>flex item</a>
+	in the <a>flex container</a>,
+	assuming it was a fixed size box of its used size.
 
 	For example, by default, the static position of absolutely positioned elements is in the main-start/column-start corner,
 	corresponding to the default values of 'justify-self' and 'align-self'.