ServiceWorker: check if StopWorker is called twice

content/renderer/service_worker/embedded_worker_dispatcher.cc

 // Copyright 2013 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 "content/renderer/service_worker/embedded_worker_dispatcher.h"
 
 #include <memory>
 
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/string16.h"
@@ skipping 59 matching lines @@
       params, base::MakeUnique<ServiceWorkerContextClient>(
                   params.embedded_worker_id, params.service_worker_version_id,
                   params.scope, params.script_url,
                   params.worker_devtools_agent_route_id, nullptr));
   RegisterWorker(params.embedded_worker_id, std::move(wrapper));
 }
 
 void EmbeddedWorkerDispatcher::OnStopWorker(int embedded_worker_id) {
   TRACE_EVENT0("ServiceWorker", "EmbeddedWorkerDispatcher::OnStopWorker");
   WorkerWrapper* wrapper = workers_.Lookup(embedded_worker_id);
-  DCHECK(wrapper);
+  // OnStopWorker is possible to be called twice.
+  if (!wrapper) {
+    LOG(WARNING) << "Got OnStopWorker for nonexistent worker";
+    return;
+  }
   // This should eventually call WorkerContextDestroyed. (We may need to post
   // a delayed task to forcibly abort the worker context if we find it
   // necessary)
   stop_worker_times_[embedded_worker_id] = base::TimeTicks::Now();
   wrapper->worker()->terminateWorkerContext();
 }
 
 void EmbeddedWorkerDispatcher::OnResumeAfterDownload(int embedded_worker_id) {
   TRACE_EVENT0("ServiceWorker",
                "EmbeddedWorkerDispatcher::OnResumeAfterDownload");
@@ skipping 78 matching lines @@
 void EmbeddedWorkerDispatcher::RecordStopWorkerTimer(int embedded_worker_id) {
   WorkerWrapper* wrapper = workers_.Lookup(embedded_worker_id);
   DCHECK(wrapper);
   // This should eventually call WorkerContextDestroyed. (We may need to post
   // a delayed task to forcibly abort the worker context if we find it
   // necessary)
   stop_worker_times_[embedded_worker_id] = base::TimeTicks::Now();
 }
 
 }  // namespace content