Reland "Implement random wallpaper feature"

chrome/browser/resources/options2/chromeos/set_wallpaper_options.css

 /* Copyright (c) 2012 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. */
 
 #wallpaper-title span {
   -webkit-padding-start: 17px;
   padding-top: 6px;
 }
 
 #set-wallpaper-page .content-area {
   height: 400px;
 }
 
 #wallpaper-grid {
   margin: 0;
   width: 640px;
 }
 
 #wallpaper-grid img {
   height: 80px;
   width: 128px;
 }
 
+.grayout img {
+  -webkit-filter: opacity(50%);
+}
+
 .bottom-bar {
-  -webkit-box-orient: horizontal;
+  -webkit-box-orient: vertical;
   display: -webkit-box;
 }
 
 .bottom-bar .spacer {
   -webkit-box-flex: 1;
 }
 
 .image-attr {
+  -webkit-padding-start: 34px;
   line-height: 26px;
-  padding: 14px 0 14px 34px;
+  padding-top: 14px;
 }
 
 #author-website {
   -webkit-padding-start: 5px;
 }
+
+#wallpaper-action-area {
+  -webkit-padding-start: 34px;
+  padding-top: 0;
+}