Unify iron-dropdown CSS

chrome/browser/resources/settings/settings_shared_css.html

Index: chrome/browser/resources/settings/settings_shared_css.html
diff --git a/chrome/browser/resources/settings/settings_shared_css.html b/chrome/browser/resources/settings/settings_shared_css.html
index a04010cd17536ac42079476780000fd5e90f8298..859c59a3e3dbe9962badc4fd853906394d239a40 100644
--- a/chrome/browser/resources/settings/settings_shared_css.html
+++ b/chrome/browser/resources/settings/settings_shared_css.html
@@ -55,6 +55,19 @@
         outline: none;
       }
 
+      iron-dropdown .dropdown-content {
+        background-color: white;
+        box-shadow: 0 2px 6px var(--paper-grey-500);
+      }
+
+      iron-dropdown .dropdown-content paper-item {
+        @apply(--settings-actionable);
+      }
+
+      iron-dropdown .dropdown-content paper-item:hover {
+        background-color: var(--settings-hover-color);
+      }
+
       span ~ a {
         -webkit-margin-start: 4px;
       }