Create a histogram serialization mechanism in components/metrics

components/metrics/histogram_sample_chromeos.cc

Index: components/metrics/histogram_sample_chromeos.cc
diff --git a/components/metrics/histogram_sample_chromeos.cc b/components/metrics/histogram_sample_chromeos.cc
new file mode 100644
index 0000000000000000000000000000000000000000..955b902086eb1fc58e811da8246c5f5f60845329
--- /dev/null
+++ b/components/metrics/histogram_sample_chromeos.cc
@@ -0,0 +1,60 @@
+// 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.
+
+#include "components/metrics/histogram_sample_chromeos.h"
+
+#include <string>
+
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_split.h"
+#include "base/strings/stringprintf.h"
+#include "components/metrics/metric_sample_chromeos.h"
+
+using base::SplitString;
+using base::StringPrintf;
+using base::StringToInt;
+using std::string;
+using std::vector;
+
+namespace metrics {
+
+HistogramSample::HistogramSample(const std::string& name,
+                                 int sample,
+                                 int min,
+                                 int max,
+                                 int nbucket)
+    : MetricSample(MetricSample::HISTOGRAM, name),
+      max_(max),
+      min_(min),
+      sample_(sample),

[Ben Chan, 2014/04/18 20:27:08]

nit: when possible, order the member variables in the same way as the
constructor arguments, so that one may not be mistaken than the variables are
initialized out-of-order in constructor initializer list 

+      nbucket_(nbucket) {}
+
+HistogramSample::~HistogramSample() {}
+
+string HistogramSample::ToString() const {
+  return StringPrintf("histogram%c%s %d %d %d %d%c",
+                      '\0',
+                      name().c_str(),
+                      sample_,
+                      min_,
+                      max_,
+                      nbucket_,
+                      '\0');
+}
+
+// static
+HistogramSample* HistogramSample::ReadHistogram(
+    const std::string& histogram_serialized) {
+  vector<string> parts;
+  SplitString(histogram_serialized, ' ', &parts);
+  if (parts.size() != 5) return NULL;

[Ben Chan, 2014/04/18 20:27:08]

nit: add a comment to describe the serialized format

+  int sample, min, max, nbucket;
+  if (!StringToInt(parts[1], &sample) || !StringToInt(parts[2], &min) ||
+      !StringToInt(parts[3], &max) || !StringToInt(parts[4], &nbucket))
+    return NULL;
+
+  return new HistogramSample(parts[0], sample, min, max, nbucket);

[Ben Chan, 2014/04/18 20:27:08]

I think SplitString still gives 5 components on a string like " 1 2 3 4", which
means parts[0] will be an empty string. Do you want to check parts[0]?

+}
+
+}  // namespace metrics