Adding reporting of metrics sampling rate.

chrome/browser/metrics/chrome_metrics_services_manager_client.h

 // Copyright 2015 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 CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICES_MANAGER_CLIENT_H_
 #define CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICES_MANAGER_CLIENT_H_
 
 #include <memory>
 
 #include "base/feature_list.h"
 #include "base/macros.h"
 #include "base/threading/thread_checker.h"
 #include "chrome/browser/safe_browsing/safe_browsing_service.h"
 #include "components/metrics_services_manager/metrics_services_manager_client.h"
 
 class PrefService;
 
 namespace metrics {
 class EnabledStateProvider;
 class MetricsStateManager;
 }
 
-// Metrics reporting feature. This feature, along with user consent, controls if
-// recording and reporting are enabled. If the feature is enabled, but no
-// consent is given, then there will be no recording or reporting.
-extern const base::Feature kMetricsReportingFeature;
-
 // Provides a //chrome-specific implementation of MetricsServicesManagerClient.
 class ChromeMetricsServicesManagerClient
     : public metrics_services_manager::MetricsServicesManagerClient {
  public:
   explicit ChromeMetricsServicesManagerClient(PrefService* local_state);
   ~ChromeMetricsServicesManagerClient() override;
 
+  // Determines if this client is eligible to send metrics. If they are, and
+  // there was user consent, then metrics and crashes would be reported.
+  static bool IsClientInSample();
+
+  // Gets the sample rate. If the sample rate is not defined, returns false, and
+  // |rate| is unchanged, otherwise returns true, and |rate| contains the sample
+  // rate.

[Alexei Svitkine (slow), 2016/08/01 20:28:27]

Nit: Expand comment to explain that if rate is not defined, there is no
sampling. Also mention something about this only returning a sample rate for
eligible clients.

[jwd, 2016/08/02 14:26:38]

Done.

+  static bool GetSamplingRatePerMille(int* rate);
+
  private:
   // This is defined as a member class to get access to
   // ChromeMetricsServiceAccessor through ChromeMetricsServicesManagerClient's
   // friendship.
   class ChromeEnabledStateProvider;
 
   // metrics_services_manager::MetricsServicesManagerClient:
   std::unique_ptr<rappor::RapporService> CreateRapporService() override;
   std::unique_ptr<variations::VariationsService> CreateVariationsService()
       override;
@@ skipping 22 matching lines @@
   PrefService* local_state_;
 
   // Subscription to SafeBrowsing service state changes.
   std::unique_ptr<safe_browsing::SafeBrowsingService::StateSubscription>
       sb_state_subscription_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeMetricsServicesManagerClient);
 };
 
 #endif  // CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICES_MANAGER_CLIENT_H_