Implement ServiceWorkerFetchDispatcher::MaybeStartNavigationPreload().

net/log/net_log_event_type_list.h

 // 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.
 
 // NOTE: No header guards are used, since this file is intended to be expanded
 // directly into net_log.h. DO NOT include this file anywhere else.
 
 // In the event of a failure, a many end events will have a |net_error|
 // parameter with the integer error code associated with the failure.  Most
 // of these parameters are not individually documented.
@@ skipping 2098 matching lines @@
 EVENT_TYPE(SERVICE_WORKER_START_WORKER)
 
 // The start/end of dispatching a fetch event to an activated, running service
 // worker.
 // For the END phase, the following parameters are attached:
 // {
 //   "status": The ServiceWorkerStatusCode as a string. Only present on failure.
 // }
 EVENT_TYPE(SERVICE_WORKER_FETCH_EVENT)
 
+// The start/end of dispatching a navigation preload request to the server.
+// The BEGIN phase contains the following parameters:
+// {
+//   "url": The URL that was being requested.
+// }
+// The END phase contains the following parameters:
+// {
+//   "net_error": The net error code for the failure, if any.
+// }
+EVENT_TYPE(SERVICE_WORKER_NAVIGATION_PRELOAD)
+
 // ------------------------------------------------------------------------
 // Global events
 // ------------------------------------------------------------------------
 // These are events which are not grouped by source id, as they have no
 // context.
 
 // This event is emitted whenever NetworkChangeNotifier determines that an
 // active network adapter's IP address has changed.
 EVENT_TYPE(NETWORK_IP_ADDRESSES_CHANGED)
 
@@ skipping 921 matching lines @@
 // {
 //   "current_position": <Shows current read position>,
 // }
 //
 // The END phase contains the following information:
 // {
 //   "result": <Result of reading. Result > 0 is bytes read. Result == 0 means
 //              the end of file. Result < 0 means an error.>
 // }
 EVENT_TYPE(UPLOAD_DATA_STREAM_READ)