Keep the wrapper of FetchEvent alive while waiting for the preload response.

third_party/WebKit/Source/modules/serviceworkers/FetchEvent.h

 // 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.
 
 #ifndef FetchEvent_h
 #define FetchEvent_h
 
 #include <memory>
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptPromiseProperty.h"
+#include "core/dom/ContextLifecycleObserver.h"
 #include "modules/EventModules.h"
 #include "modules/ModulesExport.h"
 #include "modules/fetch/Request.h"
 #include "modules/serviceworkers/ExtendableEvent.h"
 #include "modules/serviceworkers/FetchEventInit.h"
 #include "modules/serviceworkers/WaitUntilObserver.h"
+#include "platform/bindings/ActiveScriptWrappable.h"
 #include "platform/heap/Handle.h"
 #include "platform/loader/fetch/ResourceResponse.h"
 
 namespace blink {
 
 class ExceptionState;
 class FetchRespondWithObserver;
 class Request;
 class Response;
 class ScriptState;
 class WebDataConsumerHandle;
 struct WebServiceWorkerError;
 class WebURLResponse;
 class WorkerGlobalScope;
 
 // A fetch event is dispatched by the client to a service worker's script
 // context. FetchRespondWithObserver can be used to notify the client about the
 // service worker's response.
-class MODULES_EXPORT FetchEvent final : public ExtendableEvent {
+class MODULES_EXPORT FetchEvent final
+    : public ExtendableEvent,
+      public ActiveScriptWrappable<FetchEvent>,
+      public ContextClient {
   DEFINE_WRAPPERTYPEINFO();
+  USING_GARBAGE_COLLECTED_MIXIN(FetchEvent);
 
  public:
   using PreloadResponseProperty = ScriptPromiseProperty<Member<FetchEvent>,
                                                         Member<Response>,
                                                         Member<DOMException>>;
   static FetchEvent* Create(ScriptState*,
                             const AtomicString& type,
                             const FetchEventInit&);
   static FetchEvent* Create(ScriptState*,
                             const AtomicString& type,
                             const FetchEventInit&,
                             FetchRespondWithObserver*,
                             WaitUntilObserver*,
                             bool navigation_preload_sent);
 
+  ~FetchEvent() override;
+
   Request* request() const;
   String clientId() const;
   bool isReload() const;
 
   void respondWith(ScriptState*, ScriptPromise, ExceptionState&);
   ScriptPromise preloadResponse(ScriptState*);
 
   void OnNavigationPreloadResponse(ScriptState*,
                                    std::unique_ptr<WebURLResponse>,
                                    std::unique_ptr<WebDataConsumerHandle>);
   void OnNavigationPreloadError(ScriptState*,
                                 std::unique_ptr<WebServiceWorkerError>);
   void OnNavigationPreloadComplete(WorkerGlobalScope*,
                                    double completion_time,
                                    int64_t encoded_data_length,
                                    int64_t encoded_body_length,
                                    int64_t decoded_body_length);
 
   const AtomicString& InterfaceName() const override;
 
+  // ScriptWrappable
+  bool HasPendingActivity() const override;
+
   DECLARE_VIRTUAL_TRACE();
 
  protected:
   FetchEvent(ScriptState*,
              const AtomicString& type,
              const FetchEventInit&,
              FetchRespondWithObserver*,
              WaitUntilObserver*,
              bool navigation_preload_sent);
 
  private:
   Member<FetchRespondWithObserver> observer_;
   Member<Request> request_;
   Member<PreloadResponseProperty> preload_response_property_;
   std::unique_ptr<WebURLResponse> preload_response_;
   String client_id_;
   bool is_reload_;
 };
 
 }  // namespace blink
 
 #endif  // FetchEvent_h