[css-cascade-4][css-cascade-5] Define 'cascade-dependent keyword'. #7080

Author: tabatkins

css-cascade-4/Overview.bs

@@ -1229,6 +1229,11 @@ Explicit Defaulting</h3>
 	As specified in <a href="https://www.w3.org/TR/css-values/#common-keywords">CSS Values and Units</a> [[!css-values-3]],
 	all CSS properties can accept these values.
 
+	The keyword ''revert''
+	is a <dfn export>cascade-dependent keyword</dfn>;
+	some contexts may restrict its use
+	while allowing the other [=CSS-wide keywords=].
+
 <h4 id="initial">
 Resetting a Property: the ''initial'' keyword</h4>
 

css-cascade-5/Overview.bs

@@ -1817,6 +1817,11 @@ Explicit Defaulting</h3>
 	As specified in <a href="https://www.w3.org/TR/css-values/#common-keywords">CSS Values and Units</a> [[!css-values-3]],
 	all CSS properties can accept these values.
 
+	The keywords ''revert'' and ''revert-layer''
+	are <dfn export lt="cascade-dependent keyword">cascade-dependent keywords</dfn>;
+	some contexts may restrict their use
+	while allowing the other [=CSS-wide keywords=].
+
 <h4 id="initial">
 Resetting a Property: the ''initial'' keyword</h4>