MD WebUI: Extract settings-dialog into shared cr-dialog element

chrome/browser/resources/settings/settings_shared_css.html

+<link rel="import" href="chrome://resources/cr_elements/shared_style_css.html">
 <link rel="import" href="/settings_root_css.html">
 
 <!-- Common styles for Material Design settings. -->
 <dom-module id="settings-shared">
   <template>
-    <style>
+    <style include="cr-shared-style">
       h2 {
         align-items: center;
         display: flex;
         font-size: 100%;
         font-weight: 500;
         margin: 0;
         min-height: var(--settings-row-min-height);
       }
 
       iron-icon[icon='cr:check'],
@@ skipping 103 matching lines @@
       .text-elide {
         overflow: hidden;
         text-overflow: ellipsis;
         white-space: nowrap;
       }
 
       .button-strip {
         text-align: end;
       }
 
-      .action-button {
-        background: var(--google-blue-500);
-        color: white;
-        --paper-button-flat-keyboard-focus: {
-          background-color: rgb(58, 117, 215);  /* 88% of --google-blue-500) */
-        };
-      }
-
-      .action-button[disabled] {
-        opacity: .25;  /* TODO(dbeam): check this value with bettes. */
-      }
-
-      .cancel-button {
-        --paper-button-flat-keyboard-focus: {
-          background-color: rgba(0, 0, 0, .12);
-        };
-      }
-
-      .action-button,
-      .cancel-button {
-        font-weight: 500;
-      }
-
       /*
        * A list-frame is an outer container for list-items. It is intended to be
        * outside of a settings-box. A list-frame is likely to follow a
        * settings box.
        */
       .list-frame {
         -webkit-padding-end: 20px;
         -webkit-padding-start: 56px;
         align-items: center;
         display: block;
@@ skipping 144 matching lines @@
 
       .favicon-image {
         background-repeat: no-repeat;
         background-size: contain;
         height: 16px;
         width: 16px;
       }
     </style>
   </template>
 </dom-module>