Add CHECKs to make sure ThreadableLoader has not been created multiple times

third_party/WebKit/Source/core/fileapi/FileReaderLoader.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 96 matching lines @@
   options.preflightPolicy = ConsiderPreflight;
   options.crossOriginRequestPolicy = DenyCrossOriginRequests;
   // FIXME: Is there a directive to which this load should be subject?
   options.contentSecurityPolicyEnforcement = DoNotEnforceContentSecurityPolicy;
   // Use special initiator to hide the request from the inspector.
   options.initiator = FetchInitiatorTypeNames::internal;
 
   ResourceLoaderOptions resourceLoaderOptions;
   resourceLoaderOptions.allowCredentials = AllowStoredCredentials;
 
+  // TODO(yhirano): Remove this CHECK once https://crbug.com/667254 is fixed.
+  CHECK(!m_loader);
   if (m_client) {
     DCHECK(!m_loader);
     m_loader = ThreadableLoader::create(*executionContext, this, options,
                                         resourceLoaderOptions);
     m_loader->start(request);
   } else {
     ThreadableLoader::loadResourceSynchronously(
         *executionContext, request, *this, options, resourceLoaderOptions);
   }
 }
@@ skipping 255 matching lines @@
 
   m_stringResult = builder.toString();
 }
 
 void FileReaderLoader::setEncoding(const String& encoding) {
   if (!encoding.isEmpty())
     m_encoding = WTF::TextEncoding(encoding);
 }
 
 }  // namespace blink