Issue #1813854 by sun, jessebeach: Simplify and improve default CSS styling for menus.

core/modules/system/system.theme-rtl.css

@@ -56,19 +56,13 @@ th {
  */
 
 ul.menu {
-  text-align:right;
-}
-ul.menu li {
-  margin: 0 0.5em 0 0;
+  margin-left: 0;
+  margin-right: 1em;
+  text-align: right;
 }
-ul li.collapsed {
+.menu .collapsed {
   list-style-image: url(../../misc/menu-collapsed-rtl.png);
 }
-li.expanded,
-li.collapsed,
-li.leaf {
-  padding: 0.2em 0 0 0.5em;
-}
 
 /**
  * Markup generated by theme_menu_local_tasks().

core/modules/system/system.theme.css

@@ -250,37 +250,26 @@ th.checkbox {
  * Markup generated by theme_menu_tree().
  */
 ul.menu {
-  border: none;
-  list-style: none;
+  list-style: none outside;
+  margin-left: 1em; /* LTR */
+  padding: 0;
   text-align: left; /* LTR */
 }
-ul.menu li {
-  margin: 0 0 0 0.5em; /* LTR */
-}
-ul li.expanded {
+.menu .expanded {
   list-style-image: url(../../misc/menu-expanded.png);
   list-style-type: circle;
 }
-ul li.collapsed {
+.menu .collapsed {
   list-style-image: url(../../misc/menu-collapsed.png); /* LTR */
   list-style-type: disc;
 }
-ul li.leaf {
-  list-style-image: url(../../misc/menu-leaf.png);
-  list-style-type: square;
-}
-li.expanded,
-li.collapsed,
-li.leaf {
-  padding: 0.2em 0.5em 0 0; /* LTR */
+ul.menu li {
+  padding-top: 0.2em;
   margin: 0;
 }
-li a.active {
+ul.menu a.active {
   color: #000;
 }
-td.menu-disabled {
-  background: #ccc;
-}
 
 /**
  * Markup generated by theme_links().

core/themes/seven/reset.css

@@ -72,7 +72,6 @@ tr,
 th,
 td,
 /* Drupal: system-menus.css */
-td.menu-disabled,
 ul.links,
 ul.links.inline,
 ul.links li,