Add support for starting an extension print job to print preview

chrome/browser/resources/print_preview/data/print_ticket_store.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';
 
   // TODO(rltoscano): Maybe clear print ticket when destination changes. Or
   // better yet, carry over any print ticket state that is possible. I.e. if
   // destination changes, the new destination might not support duplex anymore,
@@ skipping 388 matching lines @@
                   print_preview.ticket_items.MarginsType.Value.CUSTOM) ||
               this.customMargins_.isValid());
     },
 
     /**
      * Creates an object that represents a Google Cloud Print print ticket.
      * @param {!print_preview.Destination} destination Destination to print to.
      * @return {!Object} Google Cloud Print print ticket.
      */
     createPrintTicket: function(destination) {
-      assert(!destination.isLocal || destination.isPrivet,
+      assert(!destination.isLocal ||
+             destination.isPrivet || destination.isExtension,
              'Trying to create a Google Cloud Print print ticket for a local ' +
-                 ' non-privet destination');
+                 ' non-privet and non-extension destination');
 
       assert(destination.capabilities,
              'Trying to create a Google Cloud Print print ticket for a ' +
                  'destination with no print capabilities');
       var cjt = {
         version: '1.0',
         print: {}
       };
       if (this.collate.isCapabilityAvailable() && this.collate.isUserEdited()) {
         cjt.print.collate = {collate: this.collate.getValue()};
@@ skipping 132 matching lines @@
     onDocumentInfoChange_: function() {
       cr.dispatchSimpleEvent(this, PrintTicketStore.EventType.DOCUMENT_CHANGE);
     },
   };
 
   // Export
   return {
     PrintTicketStore: PrintTicketStore
   };
 });