Add ref count to service workers for extension API.

content/browser/service_worker/service_worker_metrics.h

 // 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.
 
 #ifndef CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_METRICS_H_
 #define CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_METRICS_H_
 
 #include <stddef.h>
 
 #include "base/macros.h"
@@ skipping 92 matching lines @@
     FETCH_SUB_FRAME = 11,
     FETCH_SHARED_WORKER = 12,
     FETCH_SUB_RESOURCE = 13,
     UNKNOWN = 14,  // Used when event type is not known.
     FOREIGN_FETCH = 15,
     FETCH_WAITUNTIL = 16,
     FOREIGN_FETCH_WAITUNTIL = 17,
     NAVIGATION_HINT_LINK_MOUSE_DOWN = 18,
     NAVIGATION_HINT_LINK_TAP_UNCONFIRMED = 19,
     NAVIGATION_HINT_LINK_TAP_DOWN = 20,
+    // Used when external consumers want to add a request to
+    // ServiceWorkerVersion to keep it alive.
+    EXTERNAL_REQUEST = 21,
     // Add new events to record here.
     NUM_TYPES
   };
 
   // Used for UMA. Append only.
   enum class Site {
     OTHER,  // Obsolete for UMA. Use WITH_FETCH_HANDLER or
             // WITHOUT_FETCH_HANDLER.
     NEW_TAB_PAGE,
     WITH_FETCH_HANDLER,
@@ skipping 156 matching lines @@
   static void RecordStartStatusAfterFailure(int failure_count,
                                             ServiceWorkerStatusCode status);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ServiceWorkerMetrics);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_METRICS_H_