[css-pseudo] Resolve issue in favor of containing block; in <div lang=de><p lang=en>Ijk</p></div> we want to use en. Particularly important for mixed script text!

Author: fantasai

css-pseudo/Overview.bs

@@ -247,10 +247,7 @@ The ::first-letter pseudo-element</h3>
   In Dutch, for example, if the letter combination "ij" appears at the beginning of an element,
   both letters should be considered within the ''::first-letter'' pseudo-element. [[UAX29]]
   The UA should tailor its definition of <i>typographic letter unit</i>
-  to reflect the first-letter traditions of the <i>originating element</i>’s content language.
-
-  Issue: This is actually a problem in cases where the originating element is an ancestor
-  with a different content. What <em>should</em> we say here?
+  to reflect the first-letter traditions of the ''::first-letter'' pseudo-element’s <em>containing block</em>’s content language.
 
   Note: Note that the first <i>typographic letter unit</i> may in fact
   be a digit, e.g., the “6” in “67 million dollars is a lot of money.”