Merge 180450 "Avoid GCing an aborting and stopped FileReader."

Source/core/fileapi/FileReader.cpp

Index: Source/core/fileapi/FileReader.cpp
===================================================================
--- Source/core/fileapi/FileReader.cpp	(revision 181364)
+++ Source/core/fileapi/FileReader.cpp	(working copy)
@@ -243,6 +243,10 @@
 
 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();