Make the cr-settings-main fill its container

chrome/browser/resources/settings/settings_main/settings_main.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. */
 
 :host {
   background-color: rgb(219, 222, 224);
+  bottom: 0;
   color: black;
   display: block;
+  left: 0;
+  position: absolute;
+  right: 0;
+  top: 0;
 }
 
 #mainContainer {
   box-sizing: border-box;
   height: 100%;
   overflow: auto;
 }
 
 #pageContainer {
   -webkit-margin-end: 20px;
   -webkit-margin-start: 20px;
 }
 
 ::content core-icon-button {
   position: absolute;
 }