Adding reporting of metrics sampling rate.

chrome/browser/metrics/sampling_metrics_provider.cc

Index: chrome/browser/metrics/sampling_metrics_provider.cc
diff --git a/chrome/browser/metrics/sampling_metrics_provider.cc b/chrome/browser/metrics/sampling_metrics_provider.cc
new file mode 100644
index 0000000000000000000000000000000000000000..355bc4feb7c97bf7764871ba7f2fdc0e3f485ca2
--- /dev/null
+++ b/chrome/browser/metrics/sampling_metrics_provider.cc
@@ -0,0 +1,23 @@
+// Copyright 2016 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 "chrome/browser/metrics/sampling_metrics_provider.h"
+
+#include "base/metrics/sparse_histogram.h"
+#include "chrome/browser/metrics/chrome_metrics_services_manager_client.h"
+#include "components/metrics/metrics_provider.h"
+
+namespace metrics {
+
+SamplingMetricsProvider::SamplingMetricsProvider() {}
+SamplingMetricsProvider::~SamplingMetricsProvider() {}
+
+void SamplingMetricsProvider::ProvideGeneralMetrics(
+    ChromeUserMetricsExtension* uma_proto) {
+  UMA_HISTOGRAM_SPARSE_SLOWLY(
+      "UMA.SamplingRatePerMille",
+      ChromeMetricsServicesManagerClient::GetSamplingRatePerMille());
+}
+
+}  // namespace metrics