[css-inline] Inheritance of line-height (#18667)

line-height inherits, and has initial value 'normal'.
https://www.w3.org/TR/CSS2/visudet.html#propdef-line-height
diff --git a/css/css-inline/inheritance.html b/css/css-inline/inheritance.html
index 7728f67..6723c2a 100644
--- a/css/css-inline/inheritance.html
+++ b/css/css-inline/inheritance.html
@@ -23,6 +23,8 @@
 assert_inherited('initial-letters-align', 'alphabetic', 'hanging');
 assert_inherited('initial-letters-wrap', 'none', 'grid');
 assert_not_inherited('initial-sizing', 'normal', 'stretch');
+// https://www.w3.org/TR/CSS2/visudet.html#propdef-line-height
+assert_inherited('line-height', 'normal', '20px');
 assert_not_inherited('vertical-align', 'baseline', '10px');
 </script>
 </body>