Fixed WebDragData's wrong dependency.

Source/core/clipboard/DraggedIsolatedFileSystem.cpp

+// Copyright 2015 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 "config.h"
+#include "core/clipboard/DraggedIsolatedFileSystem.h"
+
+namespace blink {
+
+DraggedIsolatedFileSystem::FileSystemIdPreparationCallback DraggedIsolatedFileSystem::s_prepareCallback = nullptr;
+
+void DraggedIsolatedFileSystem::init(DraggedIsolatedFileSystem::FileSystemIdPreparationCallback callback)
+{
+    ASSERT(!s_prepareCallback);
+    s_prepareCallback = callback;
+}
+
+void DraggedIsolatedFileSystem::prepareForDataObject(DataObject* dataObject, const String& filesystemId)
+{
+    ASSERT(s_prepareCallback);
+    (*s_prepareCallback)(dataObject, filesystemId);
+}
+
+}