Simplify handling of Transferable objects while (de)serializing.

third_party/WebKit/Source/bindings/core/v8/Transferable.h

-// Copyright 2016 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 Transferable_h
-#define Transferable_h
-
-#include "core/CoreExport.h"
-
-namespace blink {
-
-class CORE_EXPORT Transferable : public GarbageCollectedFinalized<Transferable> {
-public:
-    virtual ~Transferable() { }
-    DEFINE_INLINE_VIRTUAL_TRACE() { }
-
-    enum TransferableType {
-        TransferableArrayBufferType,
-        TransferableImageBitmapType,
-        TransferableMessagePortType
-    };
-};
-
-} // namespace blink
-
-#endif // Transferable_h