[Fetch API] Request's JS wrapper should be kept alive in FetchEvent

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/ToV8.h"
+#include "bindings/core/v8/V8HiddenValue.h"
 #include "modules/fetch/Request.h"
 #include "modules/serviceworkers/ServiceWorkerGlobalScope.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 FetchEvent* FetchEvent::create()
 {
     return new FetchEvent();
 }
 
-FetchEvent* FetchEvent::create(const AtomicString& type, const FetchEventInit& initializer)
+FetchEvent* FetchEvent::create(ScriptState* scriptState, const AtomicString& type, const FetchEventInit& initializer)
 {
-    return new FetchEvent(type, initializer, nullptr);
+    return new FetchEvent(scriptState, type, initializer, nullptr);
 }
 
-FetchEvent* FetchEvent::create(const AtomicString& type, const FetchEventInit& initializer, RespondWithObserver* observer)
+FetchEvent* FetchEvent::create(ScriptState* scriptState, const AtomicString& type, const FetchEventInit& initializer, RespondWithObserver* observer)
 {
-    return new FetchEvent(type, initializer, observer);
+    return new FetchEvent(scriptState, type, initializer, observer);
 }
 
 Request* FetchEvent::request() const
 {
     return m_request;
 }
 
 String FetchEvent::clientId() const
 {
     return m_clientId;
@@ skipping 14 matching lines @@
 const AtomicString& FetchEvent::interfaceName() const
 {
     return EventNames::FetchEvent;
 }
 
 FetchEvent::FetchEvent()
     : m_isReload(false)
 {
 }
 
-FetchEvent::FetchEvent(const AtomicString& type, const FetchEventInit& initializer, RespondWithObserver* observer)
+FetchEvent::FetchEvent(ScriptState* scriptState, const AtomicString& type, const FetchEventInit& initializer, RespondWithObserver* observer)
     : ExtendableEvent(type, initializer)
     , m_observer(observer)
 {
-    if (initializer.hasRequest())
-        m_request = initializer.request();
     m_clientId = initializer.clientId();
     m_isReload = initializer.isReload();
+    if (initializer.hasRequest()) {
+        ScriptState::Scope scope(scriptState);
+        m_request = initializer.request();
+        v8::Local<v8::Value> request = toV8(m_request, scriptState);
+        v8::Local<v8::Value> event = toV8(this, scriptState);

[haraken, 2016/06/01 12:16:59]

Given that both objects have wrappers, can we use [SetWrapperReferenceFrom/To]
instead?

+        if (event.IsEmpty()) {
+            // |toV8| can return an empty handle when the worker is terminating.
+            // We don't want the renderer to crash in such cases.
+            // TODO(yhirano): Replace this branch with an assertion.
+            return;
+        }
+        DCHECK(event->IsObject());
+        // Sets an hidden value in order to teach V8 the dependency from

[haraken, 2016/06/01 12:16:59]

a hidden value

[yhirano, 2016/06/03 02:09:45]

Done.

+        // the event to the request.
+        V8HiddenValue::setHiddenValue(scriptState, event.As<v8::Object>(), V8HiddenValue::requestInFetchEvent(scriptState->isolate()), request);

[haraken, 2016/06/01 12:16:59]

yukishiino@ is replacing V8HiddenValue with V8PrivateProperty, which is much
faster. Can you try V8PrivateProperty? :)

[yhirano, 2016/06/01 12:22:51]

Does it work with M52? If this CL fixes crashes, I will want to merge it.

[Yuki, 2016/06/02 04:51:12]

No, V8PrivateProperty gets supported since M53.  Please keep using V8HiddenValue
for M52.

+        // As written above, we don't check the return value.
+        // TODO(yhirano): Add an assertion.
+    }
 }
 
 DEFINE_TRACE(FetchEvent)
 {
     visitor->trace(m_observer);
     visitor->trace(m_request);
     ExtendableEvent::trace(visitor);
 }
 
 } // namespace blink