FileReader.result attribute should use IDL union types to avoid using custom binding.

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 28 matching lines @@
 #include "platform/heap/Handle.h"
 #include "wtf/Forward.h"
 #include "wtf/RefCounted.h"
 
 namespace blink {
 
 class Blob;
 class DOMArrayBuffer;
 class ExceptionState;
 class ExecutionContext;
+class StringOrArrayBuffer;
 
 class FileReader final : public RefCountedGarbageCollectedEventTargetWithInlineData<FileReader>, public ActiveDOMObject, public FileReaderLoaderClient {
     DEFINE_WRAPPERTYPEINFO();
     DEFINE_EVENT_TARGET_REFCOUNTING_WILL_BE_REMOVED(RefCountedGarbageCollected<FileReader>);
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(FileReader);
 public:
     static FileReader* create(ExecutionContext*);
 
     virtual ~FileReader();
 
     enum ReadyState {
         EMPTY = 0,
         LOADING = 1,
         DONE = 2
     };
 
     void readAsArrayBuffer(Blob*, ExceptionState&);
     void readAsBinaryString(Blob*, ExceptionState&);
     void readAsText(Blob*, const String& encoding, ExceptionState&);
     void readAsText(Blob*, ExceptionState&);
     void readAsDataURL(Blob*, ExceptionState&);
     void abort();
 
     void doAbort();
 
     ReadyState readyState() const { return m_state; }
     FileError* error() { return m_error; }
-    FileReaderLoader::ReadType readType() const { return m_readType; }
-    PassRefPtr<DOMArrayBuffer> arrayBufferResult() const;
-    String stringResult();
+    void result(StringOrArrayBuffer& resultAttribute) const;
 
     // ActiveDOMObject
     virtual void stop() override;
     virtual bool hasPendingActivity() const override;
 
     // EventTarget
     virtual const AtomicString& interfaceName() const override;
     virtual ExecutionContext* executionContext() const override { return ActiveDOMObject::executionContext(); }
 
     // FileReaderLoaderClient
@@ skipping 41 matching lines @@
 
     OwnPtr<FileReaderLoader> m_loader;
     Member<FileError> m_error;
     double m_lastProgressNotificationTimeMS;
     int m_asyncOperationId;
 };
 
 } // namespace blink
 
 #endif // FileReader_h