Sync: Add encryption customization radio.

chrome/browser/resources/options/sync_setup_overlay.css

 /* TODO(jhawkins): Organize these by page. */
 
 #sync-setup-overlay * h4 {
-  margin: 10px 0;
+  margin: 5px 0;
 }
 
 #sync-setup-overlay * form {
   -webkit-user-select: none;
 }
 
 #sync-setup-overlay * .content-area {
   padding: 10px 15px;
 }
 
 .action-area-link-container {
   -webkit-box-flex: 1;
 }
 
-#sync-passphrase-container {
-  margin: 10px 0;
+.sync-customize-section-container {
+  margin: 5px 0 10px 0;
 }
 
 #sync-custom-passphrase {
   margin: 0 25px;
 }
 
 #sync-passphrase-message {
   color: gray;
 }
 
@@ skipping 295 matching lines @@
   display: none;
 }
 
 #learn-more-link {
   float: right;
 }
 
 html[dir='rtl'] #learn-more-link {
   float: left;
 }