Create a histogram serialization mechanism in components/metrics

components/metrics/chromeos/sparsehistogram_sample.h

+// Copyright 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.
+
+#ifndef COMPONENTS_METRICS_CHROMEOS_SPARSEHISTOGRAM_SAMPLE_H_
+#define COMPONENTS_METRICS_CHROMEOS_SPARSEHISTOGRAM_SAMPLE_H_
+
+#include <string>
+
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "components/metrics/chromeos/metric_sample.h"
+
+namespace metrics {
+
+// Represent a sparse histogram sample.
+// This class is meant to be used to serialize and deserialize a sample to send
+// it from ChromeOS to Chrome.
+class SparseHistogramSample : public MetricSample {
+ public:
+  SparseHistogramSample(const std::string& name, int sample);
+  virtual ~SparseHistogramSample();
+
+  int sample() const { return sample_; }
+
+  // Serialize a sample on the format:
+  // sparsehistogram\0|name_| |sample_|\0
+  virtual std::string ToString() const OVERRIDE;
+
+  // Deserialize a sample passed as a string.
+  // Returns a SparseHistogramSample if the deserialization works or NULL if it
+  // fails.
+  // The serialized format is a string listing |name| and |sample| separated
+  // by a space.
+  static scoped_ptr<SparseHistogramSample> ReadSparseHistogram(
+      const std::string& serialized_histogram);
+
+ private:
+  const int sample_;
+
+  DISALLOW_COPY_AND_ASSIGN(SparseHistogramSample);
+};
+
+}  // namespace metrics
+
+#endif  // COMPONENTS_METRICS_CHROMEOS_SPARSEHISTOGRAM_SAMPLE_H_