Use device Robot Account to access Cloud Print.

chrome/browser/resources/print_preview/data/user_info.js

 // 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.
 
 cr.define('print_preview', function() {
   'use strict';
 
   /**
    * Repository which stores information about the user. Events are dispatched
    * when the information changes.
@@ skipping 54 matching lines @@
       this.tracker_.removeAll();
     },
 
     /**
      * Called when a Google Cloud Print printer search completes. Updates user
      * information.
      * @type {cr.Event} event Contains information about the logged in user.
      * @private
      */
     onCloudPrintSearchDone_: function(event) {
-      this.userEmail_ = event.email;
-      cr.dispatchSimpleEvent(this, UserInfo.EventType.EMAIL_CHANGE);
+      if (event.origin == print_preview.Destination.Origin.COOKIES) {
+        this.userEmail_ = event.email;
+        cr.dispatchSimpleEvent(this, UserInfo.EventType.EMAIL_CHANGE);
+      }
     }
   };
 
   return {
     UserInfo: UserInfo
   };
 });