Avoid GCing an aborting and stopped FileReader.

Source/core/fileapi/FileReader.cpp

 /*
  * 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 225 matching lines @@
     terminate();
 }
 
 const AtomicString& FileReader::interfaceName() const
 {
     return EventTargetNames::FileReader;
 }
 
 void FileReader::stop()
 {
+    // The delayed abort task tidies up and advances to the DONE state.
+    if (m_loadingState == LoadingStateAborted)
+        return;
+
     if (hasPendingActivity())
         ThrottlingController::finishReader(executionContext(), this, ThrottlingController::removeReader(executionContext(), this));
     terminate();
 }
 
 bool FileReader::hasPendingActivity() const
 {
     return m_state == LOADING;
 }
 
@@ skipping 238 matching lines @@
     return m_loader->stringResult();
 }
 
 void FileReader::trace(Visitor* visitor)
 {
     visitor->trace(m_error);
     EventTargetWithInlineData::trace(visitor);
 }
 
 } // namespace blink