Create a histogram serialization mechanism in components/metrics

base/metrics/sparsehistogram_sample.cc

Index: base/metrics/sparsehistogram_sample.cc
diff --git a/base/metrics/sparsehistogram_sample.cc b/base/metrics/sparsehistogram_sample.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e2b878a4ff0c0a3243639a478b28e9a7f8dd6cc0
--- /dev/null
+++ b/base/metrics/sparsehistogram_sample.cc
@@ -0,0 +1,46 @@
+// Copyright (c) 2014 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 <string>
+
+#include "base/logging.h"
+#include "base/metrics/chromeos_metrics.h"
+#include "base/metrics/metric_sample.h"
+#include "base/metrics/sparsehistogram_sample.h"
+
+using std::string;
+
+namespace base {
+
+SparseHistogramSample::SparseHistogramSample(const std::string& histname,
+  int sample):
+  MetricSample(MetricSample::SPARSE_HISTOGRAM) {
+  name_ = histname;
+  sample_ = sample;
+}
+
+std::string SparseHistogramSample::name() {
+  return name_;
+}
+
+int SparseHistogramSample::sample() {
+  return sample_;
+}
+
+SparseHistogramSample* SparseHistogramSample::ReadSparseHistogram(
+    const std::string& hist_repr) {
+  int sample;
+  char name[128];
+  sscanf(hist_repr.c_str(), "%127s %d", name, &sample);
+  return new SparseHistogramSample(name, sample);
+}
+
+SparseHistogramSample::~SparseHistogramSample() {}
+
+int SparseHistogramSample::Write(int buffer_size, char* buffer) {
+  return ChromeOSMetrics::FormatSample(buffer_size, buffer,
+                              "sparsehistogram%c%s %d", '\0', name_.c_str(),
+                              sample_);
+}
+}  // namespace base