[css-pseudo-4] Better definition of inheritance from ::first-line per #1097

Author: fantasai

css-pseudo-4/Overview.bs

@@ -205,13 +205,16 @@ Styling the First Line Pseudo-element</h4>
 <h4 id="first-line-inheritance">
 Inheritance and the ''::first-line'' Pseudo-element</h4>
 
-  During CSS inheritance, the portion of a child element that occurs on the first line
-  only inherits properties applicable to the ''::first-line'' pseudo-element
+  During CSS [=inheritance=],
+  the [=box fragment|fragment=] of a child that occurs on the first line
+  inherits any standard [=inherited properties=]
   from the ''::first-line'' pseudo-element.
-  For all other properties inheritance is
-  from the non-pseudo-element parent of the first line pseudo element.
+  For all other properties,
+  including all [=custom properties=] [[!CSS-VARIABLES-1]],
+  inheritance is
+  from the non-pseudo parent.
   (The portion of a child element that does not occur on the first line
-  always inherits from the parent of that child.)
+  always inherits from the non-pseudo parent.)
 
 <h3 id="first-letter-pseudo">
 The ::first-letter pseudo-element</h3>
@@ -997,6 +1000,10 @@ Changes</h2>
   <ul>
     <li>Included spaces between the first letter and its surrounding punctuation in ''::first-letter''.
     (<a href="https://github.com/w3c/csswg-drafts/issues/5154">Issue 5154</a>)
+    <li>Define inheritance of properties from ''::first-line''
+    in terms of inheritability rather than applicability
+    and define interaction with custom properties.
+    (<a href="https://github.com/w3c/csswg-drafts/issues/1097">Issue 1097</a>)
     <li>Added ''::marker'' to types allowed for {{CSSPseudoElement}} interface.
     <li>Clarified return value of {{pseudo()}}.
     <li>Added 'content', 'unicode-bidi', and 'direction' to properties allowed on ''::marker''.