Minor note clarification

Author: fantasai

css3-flexbox/Overview.html

@@ -1284,7 +1284,8 @@ <h3 id=min-size-auto><span class=secno>4.5. </span> Implied Minimum Size of
     amounts of content, the layout engine must traverse all of this content
     before finding its minimum size, whereas if the author sets an explicit
     minimum, this is not necessary. (For items with small amounts of content,
-    however, this traversal is trivial and therefore not a problem.)
+    however, this traversal is trivial and therefore not a performance
+    concern.)
   </div>
 
   <h2 id=ordering-and-orientation><span class=secno>5. </span> Ordering and

css3-flexbox/Overview.src.html

@@ -929,7 +929,7 @@ <h3 id='min-size-auto'>
 			the layout engine must traverse all of this content before finding its minimum size,
 			whereas if the author sets an explicit minimum, this is not necessary.
 			(For items with small amounts of content, however,
-			this traversal is trivial and therefore not a problem.)
+			this traversal is trivial and therefore not a performance concern.)
 	</div>
 
 <h2>