MD WebUI: change how initial focus works in <dialog>s now that they know about shadow DOM

ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js

Index: ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
diff --git a/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js b/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
index 3e29f9fcb60fe9ee6eb56748814f412c4397903d..d15ed9b8173a769d12afe886806d1509a99cfffc 100644
--- a/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
+++ b/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.js
@@ -41,13 +41,6 @@ Polymer({
     }.bind(this));
   },
 
-  /** @override */
-  attached: function() {
-    var title = this.getContentChildren('[select=".title"]');
-    if (title.length)
-      title[0].tabIndex = -1;
-  },
-
   cancel: function() {
     this.fire('cancel');
     HTMLDialogElement.prototype.close.call(this, '');