DOMUI Prefs: Add a visual indication of the lead element

chrome/browser/resources/options/options_page.css

Index: chrome/browser/resources/options/options_page.css
diff --git a/chrome/browser/resources/options/options_page.css b/chrome/browser/resources/options/options_page.css
index 47447f4f20cca95c3efc897257eb9df4d27000df..6e04d759c9768cc6e8396f2944c8a1713641c97c 100644
--- a/chrome/browser/resources/options/options_page.css
+++ b/chrome/browser/resources/options/options_page.css
@@ -378,6 +378,22 @@ list > [selected]:hover {
   background-image: none;
 }
 
+list:focus > [lead],
+list:focus > [lead][selected] {
+  border-top: 1px solid #b2b2b2;
+  border-bottom: 1px solid #b2b2b2;
+}
+
+list:focus > [lead]:nth-child(2),
+list:focus > [lead][selected]:nth-child(2) {
+  border-top: 1px solid #f2f2f2;
+}
+
+list:focus > [lead]:nth-last-child(2),
+list:focus > [lead][selected]:nth-last-child(2) {
+  border-bottom: 1px solid #f2f2f2;
+}
+
 list[disabled] > [lead][selected],
 list[disabled]:focus > [lead][selected] {
   border: none;