ChromeOS: Implement Language 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;
 }
 
@@ skipping 15 matching lines @@
 }
 
 .header-container {
   padding: 50px 40px 18px;
 }
 
 .footer-container {
   padding: 24px 40px 34px;
 }
 
+#oobe-bottom {
+  box-shadow: 0 -1px 1px rgba(0, 0, 0, 0.14);
+  padding: 24px 40px 34px;
+  z-index: 1;
+}
+
 ::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: 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,
-