MD Settings: Restore focus after closing dialogs, for content settings.

chrome/browser/resources/settings/site_settings/site_list.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_action_menu/cr_action_menu.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/cr_elements/policy/cr_policy_pref_indicator.html">
 <link rel="import" href="chrome://resources/html/web_ui_listener_behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="../i18n_setup.html">
 <link rel="import" href="../icons.html">
 <link rel="import" href="../route.html">
@@ skipping 12 matching lines @@
         right: 8px;
       }
 
       .selectable {
         -webkit-user-select: text;
       }
     </style>
     <div id="category">
       <div class="settings-box first" hidden$="[[allSites]]">
         <h2 class="start">[[categoryHeader]]</h2>
-        <paper-button class="secondary-button header-aligned-button" id="icon"
+        <paper-button id="addSite"
+            class="secondary-button header-aligned-button"
             hidden="[[readOnlyList]]" on-tap="onAddSiteTap_">
           $i18n{add}
         </paper-button>
       </div>
 
       <dialog is="cr-action-menu">
         <button class="dropdown-item" role="option" id="allow"
             on-tap="onAllowTap_" hidden$="[[!showAllowAction_]]">
           $i18n{siteSettingsActionAllow}
         </button>
@@ skipping 60 matching lines @@
       </div>
     </div>
     <template is="dom-if" if="[[showEditExceptionDialog_]]" restamp>
       <settings-edit-exception-dialog model="[[actionMenuSite_]]"
           on-close="onEditExceptionDialogClosed_">
       </settings-edit-exception-dialog>
     </template>
   </template>
   <script src="site_list.js"></script>
 </dom-module>