Add ServiceWorker.NavigationPreload.HeaderSize UMA

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 268 matching lines @@
 
   static const char* LoadSourceToString(LoadSource source);
   static StartSituation GetStartSituation(bool is_browser_startup_complete,
                                           bool is_new_process);
 
   // Records the result of a start attempt that occurred after the worker had
   // failed |failure_count| consecutive times.
   static void RecordStartStatusAfterFailure(int failure_count,
                                             ServiceWorkerStatusCode status);
 
+  // Records the size of Service-Worker-Navigation-Preload header when the
+  // navigation preload request is to be sent.
+  static void RecordNavigationPreloadRequestHeaderSize(size_t size);
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ServiceWorkerMetrics);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_METRICS_H_