Create a histogram serialization mechanism in components/metrics

base/metrics/metrics_utils_chromeos.h

Index: base/metrics/metrics_utils_chromeos.h
diff --git a/base/metrics/metrics_utils_chromeos.h b/base/metrics/metrics_utils_chromeos.h
new file mode 100644
index 0000000000000000000000000000000000000000..e5f432a254671bb4e9c82919868ee7de91112617
--- /dev/null
+++ b/base/metrics/metrics_utils_chromeos.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_METRICS_UTILS_CHROMEOS_H_
+#define BASE_METRICS_METRICS_UTILS_CHROMEOS_H_
+
+#include "base/base_export.h"
+#include "base/memory/scoped_vector.h"
+
+namespace base {
+class MetricSample;
+
+// Contains metrics helpers to serialize and deserialize metrics collected by
+// chrome os.
+namespace MetricsUtils {
+// Deserialize a sample passed as a string and return a sample.
+// The return value will either be a subclass of MetricSample or NULL if the
+// sample could not be parsed.
+BASE_EXPORT MetricSample* ReadSample(const std::string& sample);
+
+// Read all samples from a file and truncate the file when done.
+BASE_EXPORT void ReadAndTruncateMetricsFromFile(
+    const std::string& filename,
+    ScopedVector<MetricSample>* metrics);
+
+// Serialize a metric and write it to filename.
+// The format for the message wrote is:
+//  message_size, serialized_message
+// where
+//  * message_size is the total length of the message (message_size +
+//    serialized_message) on 4 bytes
+//  * serialized_message is the serialized version of sample (using ToString)
+BASE_EXPORT bool WriteMetricToFile(const MetricSample& sample,
+                                   const std::string& filename);
+
+// Maximum length of a serialized message
+const int kMessageMaxLength = 1024;
+}  // namespace MetricsUtils
+}  // namespace base
+#endif  // BASE_METRICS_METRICS_UTILS_CHROMEOS_H_