Use tri-state enum for the existence of Fetch Handler in ServiceWorkerVersion.

content/browser/service_worker/service_worker_version.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_version.h"
 
 #include <stddef.h>
 
 #include <limits>
 #include <map>
@@ skipping 331 matching lines @@
   embedded_worker_->RemoveListener(this);
 }
 
 void ServiceWorkerVersion::SetStatus(Status status) {
   if (status_ == status)
     return;
 
   TRACE_EVENT2("ServiceWorker", "ServiceWorkerVersion::SetStatus", "Script URL",
                script_url_.spec(), "New Status", VersionStatusToString(status));
 
+  // |has_fetch_handler_| must be set before setting the status to INSTALLED,
+  // ACTIVATING or ACTIVATED.
+  DCHECK(has_fetch_handler_ ||
+         !(status == INSTALLED || status == ACTIVATING || status == ACTIVATED));
+
   status_ = status;
   if (skip_waiting_ && status_ == ACTIVATED) {
     for (int request_id : pending_skip_waiting_requests_)
       DidSkipWaiting(request_id);
     pending_skip_waiting_requests_.clear();
   }
 
   // OnVersionStateChanged() invokes updates of the status using state
   // change IPC at ServiceWorkerHandle (for JS-land on renderer process) and
   // ServiceWorkerContextCore (for devtools and serviceworker-internals).
@@ skipping 1395 matching lines @@
   ServiceWorkerMetrics::RecordTimeBetweenEvents(base::TimeTicks::Now() -
                                                 idle_time_);
 }
 
 void ServiceWorkerVersion::FinishStartWorker(ServiceWorkerStatusCode status) {
   start_worker_first_purpose_ = base::nullopt;
   RunCallbacks(this, &start_callbacks_, status);
 }
 
 }  // namespace content