ChromeOS: Implement Network Selection screen of material design OOBE.

chrome/browser/resources/chromeos/login/oobe_dialog.css

 /* Copyright 2016 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 {
   display: flex;
   flex-direction: column;
   position: relative;
 }
 
-.oobe-header {
-  background-color: var(--google-blue-500);
-  color: white;
-  height: 198px;
+.oobe-icon-div {
+ --iron-icon-height: 20px;
+ --iron-icon-width: 20px;
+ color: var(--google-blue-500);
 }
 
-:host(:not(.disabled)) .oobe-header {
-  box-shadow: 0 2px 2px 0 rgba(0, 0, 0, 0.17);
-  /* z-index is needed to make shadow visible. */
-  z-index: 1;
+.oobe-header {
+  background-color: white;
+  color: black;
+  height: 150px;
 }
 
 .oobe-footer {
   background-color: white;
   position: relative;
 }
 
 .header-container {
   padding: 50px 40px 18px;
 }
 
 .footer-container {
   padding: 24px 40px 34px;
 }
 
 ::content div.oobe-body-text {
   margin-bottom: 24px;
 }
 
 ::content div.oobe-body-text p {
   color: rgba(0, 0, 0, 0.87);
   font-size: 14px;
   line-height: 20px;
   margin: 0;
 }
 
 ::content h1.welcome-message {
-  color: white;
+  color: rgba(0, 0, 0, 0.87);
   font-size: 20px;
   font-weight: normal;
   margin-bottom: 0;
 }
 
+::content h1.welcome-message-hint {
+  color: rgba(0, 0, 0, 0.87);
+  font-size: 12px;
+  font-weight: normal;
+  margin-bottom: 0;
+}
+
 .overlay {
   background-color: rgba(0, 0, 0, 0.5);
   display: none;
   height: 100%;
   position: absolute;
   right: 0;
   top: 0;
   width: 100%;
   z-index: 11;
 }
 
 :host(.full-disabled) #full-overlay,
 :host(.disabled) #bottom-overlay,