ServiceWorker: Add null check in ServiceWorkerContextWrapper::DeleteAndStartOver

content/browser/service_worker/service_worker_context_wrapper.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/browser/service_worker/service_worker_context_wrapper.h"
 
 #include <map>
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 125 matching lines @@
   storage_partition_ = nullptr;
   process_manager_->Shutdown();
   BrowserThread::PostTask(
       BrowserThread::IO,
       FROM_HERE,
       base::Bind(&ServiceWorkerContextWrapper::ShutdownOnIO, this));
 }
 
 void ServiceWorkerContextWrapper::DeleteAndStartOver() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (!context_core_) {
+    // The context could be null due to system shutdown or restart failure. In
+    // either case, we should not have to recover the system, so just return
+    // here.
+    LOG(ERROR) << "ServiceWorkerContextCore is no longer alive.";
+    return;
+  }
   context_core_->DeleteAndStartOver(
       base::Bind(&ServiceWorkerContextWrapper::DidDeleteAndStartOver, this));
 }
 
 StoragePartitionImpl* ServiceWorkerContextWrapper::storage_partition() const {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   return storage_partition_;
 }
 
 void ServiceWorkerContextWrapper::set_storage_partition(
@@ skipping 477 matching lines @@
   observer_list_->Notify(FROM_HERE,
                          &ServiceWorkerContextObserver::OnStorageWiped);
 }
 
 ServiceWorkerContextCore* ServiceWorkerContextWrapper::context() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   return context_core_.get();
 }
 
 }  // namespace content