Migrate the one-time notice into the MD settings CBD dialog

chrome/browser/resources/settings/clear_browsing_data_dialog/clear_browsing_data_dialog.html

Index: chrome/browser/resources/settings/clear_browsing_data_dialog/clear_browsing_data_dialog.html
diff --git a/chrome/browser/resources/settings/clear_browsing_data_dialog/clear_browsing_data_dialog.html b/chrome/browser/resources/settings/clear_browsing_data_dialog/clear_browsing_data_dialog.html
index f7a6c8e08b883524e2b2dce3a20f245890316a22..dce9108a9498953d76d55a7bde9fb6ce6e148f6f 100644
--- a/chrome/browser/resources/settings/clear_browsing_data_dialog/clear_browsing_data_dialog.html
+++ b/chrome/browser/resources/settings/clear_browsing_data_dialog/clear_browsing_data_dialog.html
@@ -5,6 +5,7 @@
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-spinner/paper-spinner.html">
 <link rel="import" href="/i18n_setup.html">
 <link rel="import" href="/clear_browsing_data_dialog/clear_browsing_data_browser_proxy.html">
+<link rel="import" href="/clear_browsing_data_dialog/history_deletion_dialog.html">
 <link rel="import" href="/controls/settings_checkbox.html">
 <link rel="import" href="/controls/settings_dropdown_menu.html">
 <link rel="import" href="/icons.html">
@@ -86,7 +87,9 @@
       }
     </style>
 
-    <cr-dialog id="dialog">
+    <!-- #notice correctly places its own backdrop above #dialog and under
+         itself, so when it is shown, #dialog should not use backdrop. -->
+    <cr-dialog id="dialog" with-backdrop="[[!showHistoryDeletionDialog_]]">
       <div class="title">$i18n{clearBrowsingData}</div>
       <div class="body">
         <div class="row">
@@ -163,6 +166,12 @@
         </div>
       </div>
     </cr-dialog>
+
+    <template is="dom-if" if="[[showHistoryDeletionDialog_]]" restamp>
+      <settings-history-deletion-dialog id="notice"
+          on-iron-overlay-closed="onHistoryDeletionDialogClose_">
+      </settings-history-deletion-dialog>
+    </template>
   </template>
   <script src="clear_browsing_data_dialog.js"></script>
 </dom-module>