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

content/browser/service_worker/service_worker_version.cc

Index: content/browser/service_worker/service_worker_version.cc
diff --git a/content/browser/service_worker/service_worker_version.cc b/content/browser/service_worker/service_worker_version.cc
index c6883614eb35c96c47b14928a821698507f432b4..6170731e33d4d0923c154d7d6fa641b6d1f14109 100644
--- a/content/browser/service_worker/service_worker_version.cc
+++ b/content/browser/service_worker/service_worker_version.cc
@@ -349,6 +349,11 @@ void ServiceWorkerVersion::SetStatus(Status status) {
   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_)