Print Preview: Check capabilities before sending info ready

chrome/browser/resources/print_preview/data/destination_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';
 
   /**
    * A data store that stores destinations and dispatches events when the data
    * store changes.
@@ skipping 679 matching lines @@
      * @param {string | print_preview.DestinationOrigin} origin Destination
      *     origin.
      * @param {string} id Destination id.
      * @param {string} account User account destination is registered for.
      * @param {string} name Destination display name.
      * @param {?print_preview.Cdd} capabilities Destination capabilities.
      * @param {string} extensionId Extension ID associated with this
      *     destination.
      * @param {string} extensionName Extension name associated with this
      *     destination.
      * @private

[dpapad, 2017/06/08 01:22:14]

This function returns a boolean, but there is no @return. I am wondering how is
this not causing a compiler error. Either way, can we add an @return (and
explain what does the boolean actually mean)?

[rbpotter, 2017/06/08 22:45:09]

Done. It indicates that fetch has been started. Looks like it will
return true as long as the origin type is not PROFILE (or some non-
valid value).

      */
     fetchPreselectedDestination_: function(
         origin, id, account, name, capabilities, extensionId, extensionName) {
       this.autoSelectMatchingDestination_ =
           this.createExactDestinationMatch_(origin, id);
 
       if (origin == print_preview.DestinationOrigin.LOCAL ||
           origin == print_preview.DestinationOrigin.CROS) {
         this.nativeLayer_.startGetLocalDestinationCapabilities(id);
         return true;
@@ skipping 17 matching lines @@
         // Create a fake selectedDestination_ that is not actually in the
         // destination store. When the real destination is created, this
         // destination will be overwritten.
         this.selectedDestination_ = new print_preview.Destination(
             id,
             print_preview.DestinationType.LOCAL,
             print_preview.DestinationOrigin.PRIVET,
             name,
             false /*isRecent*/,
             print_preview.DestinationConnectionStatus.ONLINE);
-        this.selectedDestination_.capabilities = capabilities;
 
-        cr.dispatchSimpleEvent(
-          this,
-          DestinationStore.EventType.CACHED_SELECTED_DESTINATION_INFO_READY);
+        if (capabilities) {
+          this.selectedDestination_.capabilities = capabilities;
+
+          cr.dispatchSimpleEvent(
+              this,
+              DestinationStore.EventType
+                  .CACHED_SELECTED_DESTINATION_INFO_READY);
+        }
         return true;
       }
 
       if (origin == print_preview.DestinationOrigin.EXTENSION) {
         // TODO(tbarzic): Add support for requesting a single extension's
         // printer list.
         this.startLoadExtensionDestinations();
 
         this.selectedDestination_ =
             print_preview.ExtensionDestinationParser.parse({
@@ skipping 942 matching lines @@
       return this.getDestinationKey_(
           destination.origin, destination.id, destination.account);
     }
   };
 
   // Export
   return {
     DestinationStore: DestinationStore
   };
 });