MD Settings: create a global "action button" style (blue, flat)

chrome/browser/resources/settings/settings_shared_css.html

 /* Copyright 2016 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file. */
 
 /**
  * @fileoverview
  * Common styles for Material Design settings.
  */
 
 <dom-module id="settings-shared">
@@ skipping 90 matching lines @@
 
       .button-row {
         display: flex;
         margin-top: 25px;
       }
 
       .button-strip {
         text-align: end;
       }
 
+      .action-button {
+        background: var(--google-blue-500);
+        color: white;
+        font-weight: 500;
+      }
+
+      .action-button[disabled] {
+        opacity: .25;  /* TODO(dbeam): check this value with bettes. */
+      }
+
       .list-frame {
         @apply(--layout-center);
         -webkit-padding-end: 20px;
         -webkit-padding-start: 48px;
         display: block;
         padding-bottom: 0;
         padding-top: 0;
       }
 
       .list-frame select {
@@ skipping 112 matching lines @@
       .vertical-list > div:first-of-type {
         border-top: none;
       }
 
       .vertical-list > div {
         border-top: 1px solid var(--paper-grey-300);
       }
     </style>
   </template>
 </dom-module>