Move Fetch API releted code to modules/fetch.

Source/modules/serviceworkers/FetchManager.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 FetchManager_h
-#define FetchManager_h
-
-#include "bindings/core/v8/ScriptPromise.h"
-#include "wtf/HashSet.h"
-#include "wtf/OwnPtr.h"
-
-namespace blink {
-
-class ExecutionContext;
-class FetchRequestData;
-class ScriptState;
-
-class FetchManager {
-public:
-    FetchManager(ExecutionContext*);
-    ~FetchManager();
-    ScriptPromise fetch(ScriptState*, const FetchRequestData*);
-    void stop();
-    bool isStopped() const { return m_isStopped; }
-
-private:
-    class Loader;
-
-    // Removes loader from |m_loaders|.
-    void onLoaderFinished(Loader*);
-
-    ExecutionContext* m_executionContext;
-    HashSet<OwnPtr<Loader> > m_loaders;
-    bool m_isStopped;
-};
-
-} // namespace blink
-
-#endif // FetchManager_h