Create a histogram serialization mechanism in components/metrics

components/metrics/export/sparsehistogram_sample.h

Index: components/metrics/export/sparsehistogram_sample.h
diff --git a/components/metrics/export/sparsehistogram_sample.h b/components/metrics/export/sparsehistogram_sample.h
new file mode 100644
index 0000000000000000000000000000000000000000..b288c22570d88eb8854a8d8dada33e835f5ac29f
--- /dev/null
+++ b/components/metrics/export/sparsehistogram_sample.h
@@ -0,0 +1,45 @@
+// 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_EXPORT_SPARSEHISTOGRAM_SAMPLE_H_
+#define COMPONENTS_METRICS_EXPORT_SPARSEHISTOGRAM_SAMPLE_H_
+
+#include <string>
+
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "components/metrics/export/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 BASE_EXPORT SparseHistogramSample : public MetricSample {

[Alexei Svitkine (slow), 2014/05/01 15:57:09]

Remove BASE_EXPORT. Please fix throughout.

+ 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.
+  static scoped_ptr<SparseHistogramSample> ReadSparseHistogram(
+      const std::string& serialized_histogram);
+
+ private:
+  const int sample_;
+
+  DISALLOW_COPY_AND_ASSIGN(SparseHistogramSample);
+};
+
+}  // namespace metrics
+
+#endif  // COMPONENTS_METRICS_EXPORT_SPARSEHISTOGRAM_SAMPLE_H_