MD Settings: Construct reset profile dialog only when needed.

chrome/browser/resources/settings/reset_page/reset_page.css

-/* Copyright 2015 The Chromium Authors. All rights reserved.
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file. */
-
-#resetDialog {
-  min-width; 300px;
-  width: 500px;
-}
-
-#reset {
-  -webkit-margin-start: 10px;
-  -webkit-padding-end: 15px;
-  -webkit-padding-start: 15px;
-  background-color: rgb(120, 120, 120);
-  color: white;
-}
-
-#learnMore,
-#cancel {
-  color: rgb(94, 94, 94);
-}
-
-#explanation {
-  margin: 10px 0;
-}
-
-#buttonContainer {
-  margin: 15px 0;
-}
-
-#feedbackBar {
-  background-color: rgb(236, 236, 236);
-  margin: 0;
-  padding: 20px;
-}