Implement Blob.close().

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 202 matching lines @@
 }
 
 void FileReader::readInternal(Blob* blob, FileReaderLoader::ReadType type, ExceptionState& exceptionState)
 {
     // If multiple concurrent read methods are called on the same FileReader, InvalidStateError should be thrown when the state is LOADING.
     if (m_state == LOADING) {
         exceptionState.throwDOMException(InvalidStateError, "The object is already busy reading Blobs.");
         return;
     }
 
-    m_blob = blob;
+    if (blob->hasBeenClosed()) {
+        exceptionState.throwDOMException(InvalidStateError, String(blob->isFile() ? "File" : "Blob") + " has been closed.");
+        return;
+    }
+
+    // "Snapshot" the Blob data rather than the Blob itself as ongoing
+    // read operations should not be affected if close() is called on
+    // the Blob being read.
+    m_blobDataHandle = blob->blobDataHandle();
+    m_blobType = blob->type();
     m_readType = type;
     m_state = LOADING;
     m_loadingState = LoadingStatePending;
     m_error = nullptr;
     throttlingController()->pushReader(this);
 }
 
 void FileReader::executePendingRead()
 {
     ASSERT(m_loadingState == LoadingStatePending);
     m_loadingState = LoadingStateLoading;
 
     m_loader = adoptPtr(new FileReaderLoader(m_readType, this));
     m_loader->setEncoding(m_encoding);
-    m_loader->setDataType(m_blob->type());
-    m_loader->start(executionContext(), m_blob->blobDataHandle());
+    m_loader->setDataType(m_blobType);
+    m_loader->start(executionContext(), m_blobDataHandle);
+    m_blobDataHandle = nullptr;
 }
 
 static void delayedAbort(ExecutionContext*, FileReader* reader)
 {
     reader->doAbort();
 }
 
 void FileReader::abort()
 {
     WTF_LOG(FileAPI, "FileReader: aborting\n");
@@ skipping 120 matching lines @@
 }
 
 String FileReader::stringResult()
 {
     if (!m_loader || m_error)
         return String();
     return m_loader->stringResult();
 }
 
 } // namespace WebCore