Introduce FetchEventPreloadHandle to pass the preload response to FetchEvent.

content/browser/service_worker/service_worker_fetch_dispatcher.cc

Index: content/browser/service_worker/service_worker_fetch_dispatcher.cc
diff --git a/content/browser/service_worker/service_worker_fetch_dispatcher.cc b/content/browser/service_worker/service_worker_fetch_dispatcher.cc
index f3faf3e6af73f9dcafdb91c4e69cd2bdd383b605..fefc7137f6e953a3a34b43563943dc094bab16ab 100644
--- a/content/browser/service_worker/service_worker_fetch_dispatcher.cc
+++ b/content/browser/service_worker/service_worker_fetch_dispatcher.cc
@@ -8,6 +8,7 @@
 #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"
@@ -228,7 +229,7 @@ void ServiceWorkerFetchDispatcher::DispatchFetchEvent() {
   // |dispatcher| is owned by |version_|. So it is safe to pass the unretained
   // raw pointer of |version_| to OnFetchEventFinished callback.
   dispatcher->DispatchFetchEvent(
-      fetch_event_id, *request_,
+      fetch_event_id, *request_, std::move(preload_handle_),
       base::Bind(&OnFetchEventFinished, base::Unretained(version_.get()),
                  event_finish_id));
 }
@@ -270,6 +271,19 @@ void ServiceWorkerFetchDispatcher::Complete(
   fetch_callback.Run(status, fetch_result, response, version);
 }
 
+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();
+}
+
 ServiceWorkerMetrics::EventType ServiceWorkerFetchDispatcher::GetEventType()
     const {
   if (request_->fetch_type == ServiceWorkerFetchType::FOREIGN_FETCH)