Avoid GCing an aborting and stopped FileReader.

Source/core/fileapi/FileReader.cpp

Index: Source/core/fileapi/FileReader.cpp
diff --git a/Source/core/fileapi/FileReader.cpp b/Source/core/fileapi/FileReader.cpp
index 36361c26914f2c8b0ec7203419fd548a6c00028d..9ca0c46d6ae338fd25a09fa31be8ef49dd4f3b77 100644
--- a/Source/core/fileapi/FileReader.cpp
+++ b/Source/core/fileapi/FileReader.cpp
@@ -243,6 +243,10 @@ const AtomicString& FileReader::interfaceName() const
 
 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();