[MD settings] icon color and sizing centralized

chrome/browser/resources/settings/people_page/change_picture.css

 /* Copyright (c) 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. */
 
 #container {
   -webkit-margin-start: 16px;
   align-items: flex-start;
   padding-top: 16px;
 }
 
 #availableIcons img,
 #availableIcons iron-icon {
   border-radius: 4px;
   margin: 8px;
 }
 
 #availableIcons img {
   height: 64px;
   padding: 2px;
   vertical-align: top;
   width: 64px;
 }
 
 #availableIcons iron-icon {
   border: 1px solid var(--google-grey-500);
-  height: 32px;
   padding: 17px;
-  width: 32px;
 }
 
 #availableIcons .iron-selected {
   border: 2px solid var(--google-blue-500);
 }
 
 #availableIcons img.iron-selected {
   padding: 0;
 }
 
@@ skipping 25 matching lines @@
   padding: 8px;
 }
 
 #discardOldImage {
   background-color: var(--paper-red-500);
   border-radius: 50%;
   color: white;
   display: block;
   margin: 0 auto 0 auto;
 }