Print Preview: Show error message if text is typed in Copies section

chrome/browser/resources/print_preview/settings/copies_settings.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';
 
   /**
    * Component that renders the copies settings UI.
    * @param {!print_preview.ticket_items.Copies} copiesTicketItem Used to read
@@ skipping 132 matching lines @@
       this.updateUiStateInternal();
     },
 
     /**
      * Called after a timeout after user input into the textfield.
      * @private
      */
     onTextfieldTimeout_: function() {
       this.textfieldTimeout_ = null;
       var copiesVal = this.inputField_.value;
-      if (copiesVal != '') {
-        this.copiesTicketItem_.updateValue(copiesVal);
-      }
+      this.copiesTicketItem_.updateValue(copiesVal);
     },
 
     /**
      * Called when a key is pressed on the custom input.
      * @param {Event} event Contains the key that was pressed.
      * @private
      */
     onTextfieldKeyDown_: function(event) {
       if (event.keyCode != 'Enter')
         return;
@@ skipping 43 matching lines @@
       this.collateTicketItem_.updateValue(
           this.getChildElement('input.collate').checked);
     }
   };
 
   // Export
   return {
     CopiesSettings: CopiesSettings
   };
 });