[css-text] Switch word-break: break-all to use UAX14 notion of “letter”, and treat them all as ideographic.

Author: fantasai

css-text/Overview.bs

@@ -1006,9 +1006,12 @@ Line Breaking Details</h3>
 
       <dt><dfn>break-all</dfn></dt>
       <dd>Breaking is allowed within “words”:
-        in addition to ''word-break/normal'' <a>soft wrap opportunities</a>,
-        lines may break between any two <a>typographic letter units</a>
-        (except where forbidden by the 'line-break' property).
+        in addition to ''word-break/normal'' <a>soft wrap opportunities</a>:
+        specifically, any <a>typographic character units</a> resolving to the
+        <code>NU</code> (“numeric”), <code>AL</code> (“alphabetic”), or <code>SA</code> (“Southeast Asian”)
+        line breaking classes [[!UAX14]]
+        are instead treated as <code>ID</code> (“ideographic characters”)
+        for the purpose of line-breaking.
         Hyphenation is not applied. This option is used mostly in a context where
         the text consists predominantly of CJK characters with only short non-CJK excerpts,
         and it is desired that the text be better distributed on each line.</dd>
@@ -2744,6 +2747,8 @@ Changes</h2>
     <li>Made 'text-align' a shorthand of 'text-align-last' and the new 'text-align-all' property.
     <li>Removed dependence of 'text-align-last' on ''text-align: justify'',
         since the problem it solves is now solved by the shorthanding relationship.
+    <li>For ''word-break: break-all'', switched to UAX14 notion of “letters”,
+        since that handles symbols better.
   </ul>
 
   <h3 class="no-num" id="changes-2013">