Clarify UA-defined splitting of a prioritization level.

Author: fantasai

css3-text/Overview.html

@@ -2519,7 +2519,8 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
    characters at a higher priority than Latin characters), word spaces
    traditionally have a higher priority than inter-CJK spacing, and the UA
    may split the 1st-priority level to implement that. However the UA is not
-   allowed to drop spaces to the same priority as Latin characters.
+   allowed to drop either spaces or CJK characters to the same priority as
+   Latin characters.
 
   <p id=justify-symbols>The <dfn id=punctuation-symbols>symbols</dfn>
    category represents the expansion opportunities existing at or between any

css3-text/Overview.src.html

@@ -1808,8 +1808,8 @@ <h3 id="text-justify">
       justification (which treats CJK characters at a higher priority than
       Latin characters), word spaces traditionally have a higher priority
       than inter-CJK spacing, and the UA may split the 1st-priority level
-      to implement that. However the UA is not allowed to drop spaces to
-      the same priority as Latin characters.
+      to implement that. However the UA is not allowed to drop either spaces
+      or CJK characters to the same priority as Latin characters.
     <p id="justify-symbols">The <dfn id="punctuation-symbols">symbols</dfn>
       category represents the expansion opportunities existing at or between
       any pair of characters from the Unicode Symbols (S*) and Punctuation (P*)