Measuring data use of different ModelTypes in Sync Service.

sync/util/data_type_histogram.cc

+// 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.
+
+#include "sync/util/data_type_histogram.h"
+
+#include "base/metrics/sparse_histogram.h"
+
+void SyncRecordDatatypeBin(const std::string& name, int sample, int value) {
+  base::HistogramBase* histogram = base::SparseHistogram::FactoryGet(
+      name, base::HistogramBase::kUmaTargetedHistogramFlag);
+  histogram->AddCount(sample, value);
+}