[Merge to M59] Keep the wrapper of FetchEvent alive while waiting for the preload response.

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

 // 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 "modules/serviceworkers/FetchEvent.h"
 
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/ToV8ForCore.h"
 #include "bindings/core/v8/V8PrivateProperty.h"
 #include "core/dom/ExecutionContext.h"
@@ skipping 49 matching lines @@
 }
 
 ScriptPromise FetchEvent::preloadResponse(ScriptState* script_state) {
   return preload_response_property_->Promise(script_state->World());
 }
 
 const AtomicString& FetchEvent::InterfaceName() const {
   return EventNames::FetchEvent;
 }
 
+bool FetchEvent::HasPendingActivity() const {
+  // Prevent V8 from garbage collecting the wrapper object while waiting for the
+  // preload response. This is in order to keep the resolver of preloadResponse
+  // Promise alive.
+  return preload_response_property_->GetState() ==
+             PreloadResponseProperty::kPending &&
+         GetExecutionContext();
+}
+
 FetchEvent::FetchEvent(ScriptState* script_state,
                        const AtomicString& type,
                        const FetchEventInit& initializer,
                        FetchRespondWithObserver* respond_with_observer,
                        WaitUntilObserver* wait_until_observer,
                        bool navigation_preload_sent)
     : ExtendableEvent(type, initializer, wait_until_observer),
+      ContextClient(ExecutionContext::From(script_state)),
       observer_(respond_with_observer),
       preload_response_property_(new PreloadResponseProperty(
           ExecutionContext::From(script_state),
           this,
           PreloadResponseProperty::kPreloadResponse)) {
   if (!navigation_preload_sent)
     preload_response_property_->ResolveWithUndefined();
 
   client_id_ = initializer.clientId();
   is_reload_ = initializer.isReload();
@@ skipping 13 matching lines @@
     // Sets a hidden value in order to teach V8 the dependency from
     // the event to the request.
     V8PrivateProperty::GetFetchEventRequest(script_state->GetIsolate())
         .Set(event.As<v8::Object>(), request);
     // From the same reason as above, setHiddenValue can return false.
     // TODO(yhirano): Add an assertion that it returns true once the
     // graceful shutdown mechanism is introduced.
   }
 }
 
+FetchEvent::~FetchEvent() {}
+
 void FetchEvent::OnNavigationPreloadResponse(
     ScriptState* script_state,
     std::unique_ptr<WebURLResponse> response,
     std::unique_ptr<WebDataConsumerHandle> data_consume_handle) {
   if (!script_state->ContextIsValid())
     return;
   DCHECK(preload_response_property_);
   ScriptState::Scope scope(script_state);
   FetchResponseData* response_data =
       data_consume_handle
@@ skipping 29 matching lines @@
   DCHECK(preload_response_property_);
   preload_response_property_->Reject(
       ServiceWorkerError::Take(nullptr, *error.get()));
 }
 
 DEFINE_TRACE(FetchEvent) {
   visitor->Trace(observer_);
   visitor->Trace(request_);
   visitor->Trace(preload_response_property_);
   ExtendableEvent::Trace(visitor);
+  ContextClient::Trace(visitor);
 }
 
 }  // namespace blink