[css-align] Clarify that content alignment won't cut off scrollable content: 'flex-flow:column-reverse;justify-content:flex-start' should work the same as 'flex-flex:column;justify-content:flex-end'.

Author: tabatkins

css-align/Overview.bs

@@ -839,6 +839,9 @@ Overflow and Scroll Positions</h3>
 	In other words,
 	the <a>scrollable overflow region</a> is aligned relative to the viewport
 	as specified by the <a>content distribution property</a>.
+	Additionally, so that the content remains in the <a>scrollable overflow region</a> in order to be scrollable,
+	the ''overflow/scroll'' and ''overflow/auto'' values of 'overflow'
+	trigger safe content alignment always.
 
 	<div class='example'>
 		For example,
@@ -848,10 +851,6 @@ Overflow and Scroll Positions</h3>
 		and its content will overflow its main-start edge.
 	</div>
 
-	Issue: This needs to be integrated with overflow-anchor, when the property exists,
-	so that you get the same behavior whether an elements *starts out* overflowing,
-	or is filled element-by-element.
-
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