ServiceWorker: Ensure live registration during starting worker

content/browser/service_worker/service_worker_dispatcher_host.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_dispatcher_host.h"
 
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/trace_event/trace_event.h"
 #include "content/browser/message_port_message_filter.h"
@@ skipping 576 matching lines @@
       GetContext()->GetProviderHost(render_process_id_, provider_id);
   if (!provider_host) {
     BadMessageReceived();
     return;
   }
   if (!provider_host->IsContextAlive())
     return;
   if (!provider_host->SetHostedVersionId(version_id))
     BadMessageReceived();
 
-  // Retrieve the registration associated with |version_id|.
   ServiceWorkerVersion* version = GetContext()->GetLiveVersion(version_id);
   if (!version)
     return;
+
+  // Retrieve the registration associated with |version|. The registration
+  // must be alive because the version keeps it during starting worker.
   ServiceWorkerRegistration* registration =
       GetContext()->GetLiveRegistration(version->registration_id());
   DCHECK(registration);
   // TODO(ksakamoto): This is a quick fix for crbug.com/459916.
   if (!registration)
     return;
 
   // Set the document URL to the script url in order to allow
   // register/unregister/getRegistration on ServiceWorkerGlobalScope.
   provider_host->SetDocumentUrl(version->script_url());
@@ skipping 403 matching lines @@
   ServiceWorkerHandle* handle = handles_.Lookup(handle_id);
   if (!handle) {
     BadMessageReceived();
     return;
   }
   handle->version()->StopWorker(
       base::Bind(&ServiceWorkerUtils::NoOpStatusCallback));
 }
 
 }  // namespace content