[css-break] Clarify that overflow fragments just like regular content.

Author: fantasai

css-break/Overview.html

@@ -446,10 +446,10 @@ <h3 id=parallel-flows><span class=secno>2.1. </span> Parallel Fragmentation
   </ul>
 
   <p> Content overflowing the content edge of a fixed-size box is considered
-   parallel to the content after the fixed-size box. Note however that
-   content <em>not</em> overflowing the content edge of a fixed-size box is
-   embedded within the same flow as the in-flow content after it. (The
-   content edge effectively forks the fragmentation.)
+   parallel to the content after the fixed-size box. Such content fragments
+   within the context of the box's <a href="#fragmented-flow"><i>fragmented
+   flow</i></a> following normal fragmentation rules, increasing the length
+   of the <a href="#fragmented-flow"><i>fragmented flow</i></a> as necessary.
 
   <h3 id=nested-flows><span class=secno>2.2. </span> Nested Fragmentation
    Flows</h3>

css-break/Overview.src.html

@@ -214,9 +214,9 @@ <h3 id="parallel-flows">
   <p>
     Content overflowing the content edge of a fixed-size box
     is considered parallel to the content after the fixed-size box.
-    Note however that content <em>not</em> overflowing the content edge of a fixed-size box
-    is embedded within the same flow as the in-flow content after it.
-    (The content edge effectively forks the fragmentation.)
+    Such content fragments within the context of the box's <i>fragmented flow</i>
+    following normal fragmentation rules,
+    increasing the length of the <i>fragmented flow</i> as necessary.
   </p>
 
 <h3 id="nested-flows">