MD Settings: Fix pointer for paper-dropdown-menu-light.

BUG=640937,640167
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2341383002
Cr-Commit-Position: refs/heads/master@{#419292}

chrome/browser/resources/settings/settings_shared_css.html

@@ -55,9 +55,7 @@
         padding: 8px 0;
       }
 
-      iron-dropdown .dropdown-item,
-      paper-dropdown-menu-light .dropdown-item,
-      cr-shared-menu .dropdown-item {
+      .dropdown-item {
         align-items: center;
         background: none;
         border: none;
@@ -84,8 +82,7 @@
         box-shadow: 0 2px 6px var(--paper-grey-500);
       }
 
-      iron-dropdown .dropdown-content .dropdown-item:not([disabled]),
-      cr-shared-menu .dropdown-item:not([disabled]),
+      .dropdown-item:not([disabled]),
       iron-dropdown .dropdown-content paper-item {
         @apply(--settings-actionable);
       }