Create a histogram serialization mechanism in components/metrics

base/metrics/useraction_sample.h

Index: base/metrics/useraction_sample.h
diff --git a/base/metrics/useraction_sample.h b/base/metrics/useraction_sample.h
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+++ b/base/metrics/useraction_sample.h
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+// 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_CHROMEOS_USERACTION_SAMPLE_H
+#define BASE_METRICS_CHROMEOS_USERACTION_SAMPLE_H
+
+#include <string>
+
+#include "base/base_export.h"
+
+#include "base/metrics/metric_sample.h"
+
+using std::string;
+
+namespace base {
+class BASE_EXPORT UserActionSample : public MetricSample {
+ public:
+  explicit UserActionSample(const std::string& action);
+  virtual ~UserActionSample();
+  string toString() const;
+  // static
+  static UserActionSample* ReadUserAction(const std::string& message);
+};
+}  // namespace base
+#endif  // BASE_METRICS_CHROMEOS_USERACTION_SAMPLE_H