Create a histogram serialization mechanism in components/metrics

base/metrics/sparsehistogram_sample.h

Index: base/metrics/sparsehistogram_sample.h
diff --git a/base/metrics/sparsehistogram_sample.h b/base/metrics/sparsehistogram_sample.h
new file mode 100644
index 0000000000000000000000000000000000000000..e2ace07da0cc8e26bf7eb22f86b446e2e87ee886
--- /dev/null
+++ b/base/metrics/sparsehistogram_sample.h
@@ -0,0 +1,29 @@
+// 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_H
+# define BASE_METRICS_SPARSEHISTOGRAM_SAMPLE_H
+
+#include <string>
+
+#include "base/base_export.h"
+#include "base/metrics/metric_sample.h"
+
+namespace base {
+class BASE_EXPORT SparseHistogramSample: public MetricSample {
+ public:
+  SparseHistogramSample(const std::string& histname, int sample);
+  virtual ~SparseHistogramSample();
+  std::string name();
+  int sample();
+  int Write(int buffer_size, char* buffer);
+  // static
+  static SparseHistogramSample* ReadSparseHistogram(
+      const std::string& serializedhist);
+ protected:
+  std::string name_;
+  int sample_;
+};
+}  // namespace base
+# endif  // BASE_METRICS_SPARSEHISTOGRAM_SAMPLE_H