Make ThreadableLoader class to use references

Source/core/fileapi/FileReaderLoader.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 81 matching lines @@
     //   called), returns it.
     // - Otherwise, returns -1.
     long long totalBytes() const { return m_totalBytes; }
 
     FileError::ErrorCode errorCode() const { return m_errorCode; }
 
     void setEncoding(const String&);
     void setDataType(const String& dataType) { m_dataType = dataType; }
 
 private:
-    void startInternal(ExecutionContext*, const Stream*, PassRefPtr<BlobDataHandle>);
+    void startInternal(ExecutionContext&, const Stream*, PassRefPtr<BlobDataHandle>);
     void terminate();
     void cleanup();
 
     void failed(FileError::ErrorCode);
     void convertToText();
     void convertToDataURL();
 
     static FileError::ErrorCode httpStatusCodeToErrorCode(int);
 
     ReadType m_readType;
@@ skipping 25 matching lines @@
     bool m_hasRange;
     unsigned m_rangeStart;
     unsigned m_rangeEnd;
 
     FileError::ErrorCode m_errorCode;
 };
 
 } // namespace WebCore
 
 #endif // FileReaderLoader_h