Make ThrottleController an ExecutionContext supplement.

Source/core/fileapi/FileReader.h

 /*
  * Copyright (C) 2010 Google Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 21 matching lines @@
 #define FileReader_h
 
 #include "core/dom/ActiveDOMObject.h"
 #include "core/events/EventTarget.h"
 #include "core/fileapi/FileError.h"
 #include "core/fileapi/FileReaderLoader.h"
 #include "core/fileapi/FileReaderLoaderClient.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Forward.h"
 #include "wtf/RefCounted.h"
-#include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class Blob;
 class DOMArrayBuffer;
 class ExceptionState;
 class ExecutionContext;
 
 class FileReader final : public RefCountedGarbageCollectedEventTargetWithInlineData<FileReader>, public ActiveDOMObject, public FileReaderLoaderClient {
     DEFINE_WRAPPERTYPEINFO();
@@ skipping 78 matching lines @@
 
     OwnPtr<FileReaderLoader> m_loader;
     Member<FileError> m_error;
     double m_lastProgressNotificationTimeMS;
     int m_asyncOperationId;
 };
 
 } // namespace blink
 
 #endif // FileReader_h