[css-break] clarify break propagation per <http://lists.w3.org/Archives/Public/www-style/2013Dec/0331.html>

Author: fantasai

css-break/Overview.html

@@ -566,7 +566,8 @@ <h3 id=break-between><span class=secno>3.1. </span> Breaks Between Boxes:
    propagated to its container. Likewise a ‘<a href="#break-after"><code
    class=property>break-after</code></a>’ value on a last-child box is
    propagated to its container. (Conflicting values <a
-   href="#forced-breaks">combine</a> as defined below.)
+   href="#forced-breaks">combine</a> as defined below.) This propagation
+   stops before it breaks through the nearest matching fragmentation context.
 
   <p> Values for ‘<a href="#break-before"><code
    class=property>break-before</code></a>’ and ‘<a

css-break/Overview.src.html

@@ -306,6 +306,7 @@ <h3 id="break-between">
     a 'break-before' value on a first-child box is propagated to its container.
     Likewise a 'break-after' value on a last-child box is propagated to its container.
     (Conflicting values <a href="#forced-breaks">combine</a> as defined below.)
+    This propagation stops before it breaks through the nearest matching fragmentation context.
   </p>
 
   <p>