Fix the browser crash in reattaching ServiceWorker to existing DevTools window.

content/browser/devtools/service_worker_devtools_manager.cc

 // Copyright 2014 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/browser/devtools/service_worker_devtools_manager.h"
 
 #include "content/browser/devtools/devtools_manager.h"
 #include "content/browser/devtools/ipc_devtools_agent_host.h"
 #include "content/browser/devtools/service_worker_devtools_agent_host.h"
 #include "content/public/browser/browser_thread.h"
@@ skipping 73 matching lines @@
     return host->IsPausedForDebugOnStart();
   }
 
   // Worker was restarted.
   ServiceWorkerDevToolsAgentHost* agent_host = it->second;
   agent_host->WorkerRestarted(id);
   workers_.erase(it);
   workers_[id] = agent_host;
   DevToolsManager::GetInstance()->AgentHostChanged(agent_host);
 
-  return it->second->IsAttached();
+  return agent_host->IsAttached();
 }
 
 void ServiceWorkerDevToolsManager::WorkerReadyForInspection(
     int worker_process_id,
     int worker_route_id) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   const WorkerId id(worker_process_id, worker_route_id);
   AgentHostMap::iterator it = workers_.find(id);
   DCHECK(it != workers_.end());
   scoped_refptr<ServiceWorkerDevToolsAgentHost> host = it->second;
@@ skipping 64 matching lines @@
       break;
   }
   return it;
 }
 
 void ServiceWorkerDevToolsManager::ResetForTesting() {
   workers_.clear();
 }
 
 }  // namespace content