Record some foreign fetch registration metrics.

content/browser/service_worker/service_worker_metrics.cc

 // 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.
 
 #include "content/browser/service_worker/service_worker_metrics.h"
 
 #include <limits>
 #include <string>
 
 #include "base/metrics/histogram_macros.h"
@@ skipping 366 matching lines @@
                               status, SERVICE_WORKER_ERROR_MAX_VALUE);
   }
 }
 
 void ServiceWorkerMetrics::RecordInstallEventStatus(
     ServiceWorkerStatusCode status) {
   UMA_HISTOGRAM_ENUMERATION("ServiceWorker.InstallEventStatus", status,
                             SERVICE_WORKER_ERROR_MAX_VALUE);
 }
 
+void ServiceWorkerMetrics::RecordForeignFetchRegistrationCount(
+    size_t scope_count,
+    size_t origin_count) {
+  UMA_HISTOGRAM_COUNTS_100("ServiceWorker.ForeignFetch.SubScopeCount",
+                           scope_count);

[Mark P, 2016/08/11 22:42:18]

Why is the histogram "subscopecount" yet you're using a "scope_count"?  These
things sound different to me.

[Marijn Kruisselbrink, 2016/08/12 20:33:23]

Changed it to consistently be "scope count", at least on the metrics side. After
all in the spec and rest of the implementation I also call these things "foreign
fetch scopes" and not "sub scopes". 

+  if (scope_count > 0) {
+    // Only record number of origins if service worker registered for at least
+    // one foreign fetch scope.
+    UMA_HISTOGRAM_COUNTS_100("ServiceWorker.ForeignFetch.OriginCount",
+                             origin_count);
+  }
+}
+
 void ServiceWorkerMetrics::RecordEventHandledRatio(EventType event,
                                                    size_t handled_events,
                                                    size_t fired_events) {
   if (!fired_events)
     return;
   EventHandledRatioType type = EVENT_HANDLED_SOME;
   if (fired_events == handled_events)
     type = EVENT_HANDLED_ALL;
   else if (handled_events == 0)
     type = EVENT_HANDLED_NONE;
@@ skipping 278 matching lines @@
   } else if (failure_count == 2) {
     UMA_HISTOGRAM_ENUMERATION("ServiceWorker.StartWorker.AfterFailureStreak_2",
                               status, SERVICE_WORKER_ERROR_MAX_VALUE);
   } else if (failure_count == 3) {
     UMA_HISTOGRAM_ENUMERATION("ServiceWorker.StartWorker.AfterFailureStreak_3",
                               status, SERVICE_WORKER_ERROR_MAX_VALUE);
   }
 }
 
 }  // namespace content