MD Settings: Move width CSS property at the page level.

chrome/browser/resources/settings/settings_page/settings_section.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. */
 
 /**
  * @fileoverview
  * Common styles for Settings pages.
  */
 :host {
   display: block;
@@ skipping 13 matching lines @@
 
 paper-material {
   background-color: white;
   box-sizing: border-box;
   overflow: hidden;
 }
 
 paper-material,
 #placeholder {
   margin-bottom: 16px;
-  width: 605px;
 }
 
 :host(.neon-animating) paper-material {
   position: fixed;
   z-index: 1;
 }
 
 :host(.expanded) paper-material {
   margin-bottom: 0;
   min-height: 100%;
 }
 
 #placeholder {
   visibility: hidden;
 }
 
 :host(:not(.neon-animating)) #placeholder {
   position: absolute;
 }