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

third_party/WebKit/Source/modules/notifications/NotificationImageLoader.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/notifications/NotificationImageLoader.h"
 
 #include "core/dom/ExecutionContext.h"
 #include "core/fetch/ResourceLoaderOptions.h"
 #include "platform/Histogram.h"
 #include "platform/image-decoders/ImageDecoder.h"
@@ skipping 102 matching lines @@
   ResourceLoaderOptions resourceLoaderOptions;
   resourceLoaderOptions.allowCredentials = AllowStoredCredentials;
   if (executionContext->isWorkerGlobalScope())
     resourceLoaderOptions.requestInitiatorContext = WorkerContext;
 
   ResourceRequest resourceRequest(url);
   resourceRequest.setRequestContext(WebURLRequest::RequestContextImage);
   resourceRequest.setPriority(ResourceLoadPriorityMedium);
   resourceRequest.setRequestorOrigin(executionContext->getSecurityOrigin());
 
+  // TODO(yhirano): Remove this CHECK once https://crbug.com/667254 is fixed.
+  CHECK(!m_threadableLoader);
   m_threadableLoader = ThreadableLoader::create(
       *executionContext, this, threadableLoaderOptions, resourceLoaderOptions);
   m_threadableLoader->start(resourceRequest);
 }
 
 void NotificationImageLoader::stop() {
   if (m_stopped)
     return;
 
   m_stopped = true;
@@ skipping 55 matching lines @@
 void NotificationImageLoader::runCallbackWithEmptyBitmap() {
   // If this has been stopped it is not desirable to trigger further work,
   // there is a shutdown of some sort in progress.
   if (m_stopped)
     return;
 
   (*m_imageCallback)(SkBitmap());
 }
 
 }  // namespace blink