Create a histogram serialization mechanism in components/metrics

base/metrics/sparsehistogram_sample_chromeos.h

Index: base/metrics/sparsehistogram_sample_chromeos.h
diff --git a/base/metrics/sparsehistogram_sample_chromeos.h b/base/metrics/sparsehistogram_sample_chromeos.h
new file mode 100644
index 0000000000000000000000000000000000000000..88e9979de408a68d5f8222bc8e6943b44492fe8c
--- /dev/null
+++ b/base/metrics/sparsehistogram_sample_chromeos.h
@@ -0,0 +1,39 @@
+// 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.
+
+#ifndef BASE_METRICS_SPARSEHISTOGRAM_SAMPLE_CHROMEOS_H
+#define BASE_METRICS_SPARSEHISTOGRAM_SAMPLE_CHROMEOS_H
+
+#include <string>
+
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+#include "base/metrics/metric_sample_chromeos.h"
+
+namespace base {
+// Represents a sparse histogram.
+// This class is meant to be used to serialize and deserialize a sample to send
+// it from chrome os to chrome.
+class BASE_EXPORT SparseHistogramSample : public MetricSample {
+ public:
+  SparseHistogramSample(const std::string& histname, int sample);
+  virtual ~SparseHistogramSample();
+
+  int sample() const;
+  // Serialize a sample on the format:
+  // sparsehistogram\0|name_| |sample_|\0
+  virtual string ToString() const OVERRIDE;
+
+  // static
+  // Deserialize a sample passed as a string.
+  // Returns a SparseHistogramSample if the deserialization works or NULL if it
+  // fails.
+  static SparseHistogramSample* ReadSparseHistogram(
+      const std::string& serialized_histogram);
+
+ private:
+  int sample_;
+};
+}  // namespace base
+#endif  // BASE_METRICS_SPARSEHISTOGRAM_SAMPLE_CHROMEOS_H