[MD settings] css for row separator

chrome/browser/resources/settings/appearance_page/appearance_page.html

Index: chrome/browser/resources/settings/appearance_page/appearance_page.html
diff --git a/chrome/browser/resources/settings/appearance_page/appearance_page.html b/chrome/browser/resources/settings/appearance_page/appearance_page.html
index 06b4e12e732e12c0db2c387ac148866e16d5de13..693774e7cb531a513dbec3155c21cd987d487f3b 100644
--- a/chrome/browser/resources/settings/appearance_page/appearance_page.html
+++ b/chrome/browser/resources/settings/appearance_page/appearance_page.html
@@ -74,17 +74,17 @@
           </div>
 <if expr="not is_linux or chromeos">
           <template is="dom-if" if="[[prefs.extensions.theme.id.value]]">
-            <div class="secondary-action">
-              <paper-button id="useDefault" on-tap="onUseDefaultTap_"
-                  class="secondary-button">
-                $i18n{resetToDefaultTheme}
-              </paper-button>
-            </div>
+            <div class="vertical-rule-line"></div>
+            <paper-button id="useDefault" on-tap="onUseDefaultTap_"
+                class="secondary-button">
+              $i18n{resetToDefaultTheme}
+            </paper-button>
           </template>
 </if>
 <if expr="is_linux and not chromeos">
-          <div class="secondary-action" hidden="[[!showThemesSecondary_(
-            prefs.extensions.theme.id.value, useSystemTheme_)]]">
+          <div class="layout horizontal center" hidden="[[!showThemesSecondary_(
+              prefs.extensions.theme.id.value, useSystemTheme_)]]">
+            <div class="vertical-rule-line"></div>
             <template is="dom-if" if="[[showUseClassic_(
                 prefs.extensions.theme.id.value, useSystemTheme_)]]" restamp>
               <paper-button id="useDefault" on-tap="onUseDefaultTap_"