Introduce FetchEventPreloadHandle to pass the preload response to FetchEvent.

content/common/service_worker/fetch_event_dispatcher.mojom

Index: content/common/service_worker/fetch_event_dispatcher.mojom
diff --git a/content/common/service_worker/fetch_event_dispatcher.mojom b/content/common/service_worker/fetch_event_dispatcher.mojom
index e46b0e26bb6d0120fc3a794b5d700d0b1fefcf09..ff4252f1f6e1a5ebe83928472c00f58c10ea8464 100644
--- a/content/common/service_worker/fetch_event_dispatcher.mojom
+++ b/content/common/service_worker/fetch_event_dispatcher.mojom
@@ -4,14 +4,21 @@
 
 module content.mojom;
 
+import "content/common/url_loader.mojom";
 import "mojo/common/common_custom_types.mojom";
 import "third_party/WebKit/public/platform/modules/serviceworker/service_worker_event_status.mojom";
 
 [Native]
 struct ServiceWorkerFetchRequest;
 
+struct FetchEventPreloadHandle {
+  URLLoader url_loader;
+  URLLoaderClient& url_loader_client_request;
+};
+
 interface FetchEventDispatcher {
-  DispatchFetchEvent(int32 fetch_event_id, ServiceWorkerFetchRequest request)
+  DispatchFetchEvent(int32 fetch_event_id, ServiceWorkerFetchRequest request,
+                     FetchEventPreloadHandle? preload_handle)
       => (blink.mojom.ServiceWorkerEventStatus status,
           mojo.common.mojom.Time dispatch_event_time);
 };