Use device Robot Account to access Cloud Print.

chrome/browser/resources/print_preview/native_layer.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';
 
   /**
    * An interface to the native Chromium printing system layer.
    * @constructor
@@ skipping 89 matching lines @@
   NativeLayer.SERIALIZED_STATE_VERSION_ = 1;
 
   NativeLayer.prototype = {
     __proto__: cr.EventTarget.prototype,
 
     /**
      * Requests access token for cloud print requests.
      * @param {string} authType type of access token.
      */
     startGetAccessToken: function(authType) {
-      chrome.send('getAccessToken', [authType]);
+      chrome.send('getAccessToken', [/*authType*/ 'profile']);
     },
 
     /** Gets the initial settings to initialize the print preview with. */
     startGetInitialSettings: function() {
       chrome.send('getInitialSettings');
     },
 
     /**
      * Requests the system's local print destinations. A LOCAL_DESTINATIONS_SET
      * event will be dispatched in response.
@@ skipping 412 matching lines @@
 
     /**
      * Notification that access token is ready.
      * @param {string} authType Type of access token.
      * @param {string} accessToken Access token.
      * @private
      */
     onDidGetAccessToken_: function(authType, accessToken) {
       var getAccessTokenEvent = new cr.Event(
           NativeLayer.EventType.ACCESS_TOKEN_READY);
-      getAccessTokenEvent.authType = authType;
+      getAccessTokenEvent.authType = /*authType*/ 'device';
       getAccessTokenEvent.accessToken = accessToken;
       this.dispatchEvent(getAccessTokenEvent);
     },
 
     /**
      * Update the print preview when new preview data is available.
      * Create the PDF plugin as needed.
      * Called from PrintPreviewUI::PreviewDataIsAvailable().
      * @param {number} previewUid Preview unique identifier.
      * @param {number} previewResponseId The preview request id that resulted in
@@ skipping 180 matching lines @@
       return this.serializedAppStateStr_;
     }
   };
 
   // Export
   return {
     NativeInitialSettings: NativeInitialSettings,
     NativeLayer: NativeLayer
   };
 });