Implement ServiceWorkerFetchDispatcher::MaybeStartNavigationPreload().

content/browser/service_worker/service_worker_fetch_dispatcher.cc

 // 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.
 
 #include "content/browser/service_worker/service_worker_fetch_dispatcher.h"
 
 #include <string>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
 #include "content/browser/service_worker/embedded_worker_status.h"
+#include "content/browser/service_worker/service_worker_navigation_preload_fetcher.h"
 #include "content/browser/service_worker/service_worker_version.h"
 #include "content/common/service_worker/fetch_event_dispatcher.mojom.h"
 #include "content/common/service_worker/service_worker_messages.h"
 #include "content/common/service_worker/service_worker_status_code.h"
 #include "content/common/service_worker/service_worker_utils.h"
 #include "net/log/net_log.h"
 #include "net/log/net_log_capture_mode.h"
 
 #include "net/log/net_log_event_type.h"
 
@@ skipping 247 matching lines @@
 }
 
 void ServiceWorkerFetchDispatcher::MaybeStartNavigationPreload(
     net::URLRequest* original_request) {
   if (resource_type_ != RESOURCE_TYPE_MAIN_FRAME &&
       resource_type_ != RESOURCE_TYPE_SUB_FRAME) {
     return;
   }
   if (!version_->navigation_preload_enabled())
     return;
-  // TODO(horo): Implement this to start the preload request for the navigation
-  // request and set |preload_handle_|.
-  NOTIMPLEMENTED();
+  // TODO(horo): Currently NavigationPreload doesn't support request body.
+  if (!request_->blob_uuid.empty())
+    return;
+  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableExperimentalWebPlatformFeatures)) {
+    // TODO(horo): Check |version_|'s origin_trial_tokens() here if we use
+    // Origin-Trial for NavigationPreload.
+    return;
+  }
+  // TODO(horo): Pass "Service-Worker-Navigation-Preload" header to
+  // ServiceWorkerNavigationPreloadFetcher.
+  // See: https://github.com/w3c/ServiceWorker/issues/920#issuecomment-251150270
+  preload_handle_ =
+      ServiceWorkerNavigationPreloadFetcher::Start(original_request);
 }
 
 ServiceWorkerMetrics::EventType ServiceWorkerFetchDispatcher::GetEventType()
     const {
   if (request_->fetch_type == ServiceWorkerFetchType::FOREIGN_FETCH)
     return ServiceWorkerMetrics::EventType::FOREIGN_FETCH;
   return ResourceTypeToEventType(resource_type_);
 }
 
 }  // namespace content