Print Preview: Fix followup issues for removing global JS functions

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

 // Copyright 2014 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.exportPath('print_preview');
 
 /**
  * @enum {number}
  * @private
  */
@@ skipping 83 matching lines @@
     invitations: function(account) {
       return this.invitations_[account] || [];
     },
 
     /**
      * Sets the invitation store's Google Cloud Print interface.
      * @param {!cloudprint.CloudPrintInterface} cloudPrintInterface Interface
      *     to set.
      */
     setCloudPrintInterface: function(cloudPrintInterface) {
+      assert(this.cloudPrintInterface_ == null);
       this.cloudPrintInterface_ = cloudPrintInterface;
       this.tracker_.add(
           this.cloudPrintInterface_,
           cloudprint.CloudPrintInterfaceEventType.INVITES_DONE,
           this.onCloudPrintInvitesDone_.bind(this));
       this.tracker_.add(
           this.cloudPrintInterface_,
           cloudprint.CloudPrintInterfaceEventType.INVITES_FAILED,
           this.onCloudPrintInvitesDone_.bind(this));
       this.tracker_.add(
@@ skipping 101 matching lines @@
       this.invitationProcessed_(event.invitation);
       // TODO: Display an error.
       cr.dispatchSimpleEvent(
           this, InvitationStore.EventType.INVITATION_PROCESSED);
     }
   };
 
   // Export
   return {InvitationStore: InvitationStore};
 });