Update addSmbShareDialog to use cr-dialog

This change applies the migration of crrev.com/c/976394 to the
addSmbShareDialog.

Bug: 818279
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ic40afe345c38d4e776afb15f7e0fdb761f6906c0
Reviewed-on: https://chromium-review.googlesource.com/1003632Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Bailey Berro <baileyberro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551074}

chrome/browser/resources/settings/downloads_page/add_smb_share_dialog.html

@@ -12,7 +12,7 @@
 
     </style>
 
-    <dialog is="cr-dialog" id="dialog">
+    <cr-dialog id="dialog">
       <div slot="title">$i18n{addSmbShare}</div>
       <div slot="body" spellcheck="false">
         <paper-input always-float-label id="address"
@@ -30,7 +30,7 @@
             $i18n{add}
         </paper-button>
       </div>
-    </dialog>
+    </cr-dialog>
   </template>
   <script src="add_smb_share_dialog.js"></script>
 </dom-module>