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

third_party/WebKit/Source/web/WebAssociatedURLLoaderImpl.cpp

 /*
  * Copyright (C) 2010, 2011, 2012 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 392 matching lines @@
         WebURLRequest::RequestContextUnspecified) {
       // FIXME: We load URLs without setting a TargetType (and therefore a
       // request context) in several places in content/
       // (P2PPortAllocatorSession::AllocateLegacyRelaySession, for example).
       // Remove this once those places are patched up.
       newRequest.setRequestContext(WebURLRequest::RequestContextInternal);
     }
 
     Document* document = toDocument(m_observer->lifecycleContext());
     DCHECK(document);
+    // TODO(yhirano): Remove this CHECK once https://crbug.com/667254 is fixed.
+    CHECK(!m_loader);
     m_loader = DocumentThreadableLoader::create(
         *document, m_clientAdapter.get(), options, resourceLoaderOptions);
     m_loader->start(webcoreRequest);
   }
 
   if (!m_loader) {
     // FIXME: return meaningful error codes.
     m_clientAdapter->didFail(ResourceError());
   }
   m_clientAdapter->enableErrorNotifications();
@@ skipping 63 matching lines @@
   // there could be a WebURLLoader instance behind the
   // DocumentThreadableLoader instance. So, for safety, we chose to just
   // crash here.
   CHECK(ThreadState::current());
 
   m_observer->dispose();
   m_observer = nullptr;
 }
 
 }  // namespace blink