Gracefully handle FileReader() read operations when in a detached state.

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 82 matching lines @@
     DEFINE_ATTRIBUTE_EVENT_LISTENER(loadstart);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(progress);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(load);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(abort);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(error);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(loadend);
 
     virtual void trace(Visitor*) OVERRIDE;
 
 private:
+    explicit FileReader(ExecutionContext*);
+
     class ThrottlingController;
 
-    FileReader(ExecutionContext*);
-
     void terminate();
     void readInternal(Blob*, FileReaderLoader::ReadType, ExceptionState&);
     void fireErrorEvent(int httpStatusCode);
     void fireEvent(const AtomicString& type);
 
-    ThrottlingController* throttlingController();
     void executePendingRead();
 
     ReadyState m_state;
 
     // Internal loading state, which could differ from ReadyState as it's
     // for script-visible state while this one's for internal state.
     enum LoadingState {
         LoadingStateNone,
         LoadingStatePending,
         LoadingStateLoading,
         LoadingStateAborted
     };
     LoadingState m_loadingState;
 
     String m_blobType;
     RefPtr<BlobDataHandle> m_blobDataHandle;
     FileReaderLoader::ReadType m_readType;
     String m_encoding;
 
     OwnPtr<FileReaderLoader> m_loader;
     RefPtrWillBeMember<FileError> m_error;
     double m_lastProgressNotificationTimeMS;
 };
 
 } // namespace WebCore
 
 #endif // FileReader_h