Add Sparse Histogram Support to metricsPrivate

chrome/browser/extensions/api/metrics_private/metrics_private_api.cc

Index: chrome/browser/extensions/api/metrics_private/metrics_private_api.cc
diff --git a/chrome/browser/extensions/api/metrics_private/metrics_private_api.cc b/chrome/browser/extensions/api/metrics_private/metrics_private_api.cc
index 3265bb45674e5576a22b244c86df0f33357aafa3..6493f4246fe8d28a3094933904ff465d73e5aeea 100644
--- a/chrome/browser/extensions/api/metrics_private/metrics_private_api.cc
+++ b/chrome/browser/extensions/api/metrics_private/metrics_private_api.cc
@@ -8,6 +8,7 @@
 
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
+#include "base/metrics/sparse_histogram.h"
 #include "chrome/browser/metrics/metrics_service.h"
 #include "chrome/common/extensions/api/metrics_private.h"
 #include "components/variations/variations_associated_data.h"
@@ -22,6 +23,7 @@ namespace GetVariationParams = api::metrics_private::GetVariationParams;
 namespace GetFieldTrial = api::metrics_private::GetFieldTrial;
 namespace RecordUserAction = api::metrics_private::RecordUserAction;
 namespace RecordValue = api::metrics_private::RecordValue;
+namespace RecordSparseValue = api::metrics_private::RecordSparseValue;
 namespace RecordPercentage = api::metrics_private::RecordPercentage;
 namespace RecordCount = api::metrics_private::RecordCount;
 namespace RecordSmallCount = api::metrics_private::RecordSmallCount;
@@ -127,6 +129,16 @@ bool MetricsPrivateRecordValueFunction::RunImpl() {
                      params->metric.buckets, params->value);
 }
 
+bool MetricsPrivateRecordSparseValueFunction::RunImpl() {
+  scoped_ptr<RecordSparseValue::Params> params(
+      RecordSparseValue::Params::Create(*args_));
+  EXTENSION_FUNCTION_VALIDATE(params.get());
+  // This particular UMA_HISTOGRAM_ macro is okay for
+  // non-runtime-constant strings.
+  UMA_HISTOGRAM_SPARSE_SLOWLY(params->metric_name, params->value);
+  return true;
+}
+
 bool MetricsPrivateRecordPercentageFunction::RunImpl() {
   scoped_ptr<RecordPercentage::Params> params(
       RecordPercentage::Params::Create(*args_));