MD Settings: Tweak action menu styling to match the mocks.

ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.html

Index: ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.html
diff --git a/ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.html b/ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.html
index bee8924eca8b1275ee1f7c045c58974c2201f5e8..e5d4ef904c9a9757d0f5b7662db1d4dc9a807222 100644
--- a/ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.html
+++ b/ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.html
@@ -9,12 +9,17 @@
         box-shadow: 0 2px 6px var(--paper-grey-500);
         margin: 0;
         outline: none;
-        padding: 0;
+        padding: 8px 0;
       }
 
       :host::backdrop {
         background-color: transparent;
       }
+
+      :host ::content .dropdown-item:focus {
+        background-color: var(--paper-grey-300);
+        outline: none;
+      }
     </style>
     <content select=".dropdown-item,hr"></content>
   </template>