Introduce chrome://flags/#network-prediction-options-for-service-worker

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 <map>
 #include <set>
@@ skipping 104 matching lines @@
     // NAVIGATION_HINT_LINK_TAP_UNCONFIRMED = 19,  // Obsolete
     // NAVIGATION_HINT_LINK_TAP_DOWN = 20,  // Obsolete
     // Used when external consumers want to add a request to
     // ServiceWorkerVersion to keep it alive.
     EXTERNAL_REQUEST = 21,
     PAYMENT_REQUEST = 22,
     BACKGROUND_FETCH_ABORT = 23,
     BACKGROUND_FETCH_CLICK = 24,
     BACKGROUND_FETCH_FAIL = 25,
     BACKGROUND_FETCHED = 26,
+    PRECONNECT = 27,
     // 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 217 matching lines @@
 
   static void RecordRuntime(base::TimeDelta time);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ServiceWorkerMetrics);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_METRICS_H_