Start to implement FetchEvent for ServiceWorker

Source/modules/serviceworkers/RespondWithObserver.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 RespondWithObserver_h
+#define RespondWithObserver_h
+
+#include "core/dom/ContextLifecycleObserver.h"
+#include "wtf/Forward.h"
+#include "wtf/RefCounted.h"
+
+namespace WebCore {
+
+class ExecutionContext;
+class Response;
+class ScriptValue;
+
+// This class observes the service worker's handling of a FetchEvent and
+// notifies the client.
+class RespondWithObserver FINAL : public ContextLifecycleObserver, public RefCounted<RespondWithObserver> {
+public:
+    static PassRefPtr<RespondWithObserver> create(ExecutionContext*, int eventID);
+
+    ~RespondWithObserver();
+
+    void didDispatchEvent();
+
+    // Observes the promise and delays calling didHandleFetchEvent() until the
+    // given promise is resolved or rejected.
+    void respondWith(const ScriptValue&);
+
+    void responseWasRejected();
+    void responseWasFulfilled(const ScriptValue&);
+
+private:
+    class ThenFunction;
+
+    RespondWithObserver(ExecutionContext*, int eventID);
+
+    // Sends a response back to the client. The null response means to fallback
+    // to native.
+    void sendResponse(PassRefPtr<Response>);
+
+    int m_eventID;
+
+    enum State { Initial, Pending, Done };
+    State m_state;
+};
+
+} // namespace WebCore
+
+#endif // RespondWithObserver_h
+