Adding reporting of metrics sampling rate.

chrome/browser/metrics/chrome_metrics_services_manager_client.h

Index: chrome/browser/metrics/chrome_metrics_services_manager_client.h
diff --git a/chrome/browser/metrics/chrome_metrics_services_manager_client.h b/chrome/browser/metrics/chrome_metrics_services_manager_client.h
index 51bfe205ad34fa1b82bb5d9aa6963f687102c95b..b074353879ebeaf929de341441239d719bb2677f 100644
--- a/chrome/browser/metrics/chrome_metrics_services_manager_client.h
+++ b/chrome/browser/metrics/chrome_metrics_services_manager_client.h
@@ -20,11 +20,6 @@ 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 {
@@ -32,6 +27,15 @@ class ChromeMetricsServicesManagerClient
   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