Create a histogram serialization mechanism in components/metrics

components/metrics/export/sparsehistogram_sample.cc

Index: components/metrics/export/sparsehistogram_sample.cc
diff --git a/components/metrics/export/sparsehistogram_sample.cc b/components/metrics/export/sparsehistogram_sample.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b0f6c6117ca00b80c3ad9c0aa60c5b0b33dc2cb1
--- /dev/null
+++ b/components/metrics/export/sparsehistogram_sample.cc
@@ -0,0 +1,50 @@
+// 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/export/sparsehistogram_sample.h"
+
+#include <string>
+#include <vector>
+
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_split.h"
+#include "base/strings/stringprintf.h"
+#include "components/metrics/export/metric_sample.h"
+
+using base::SplitString;
+using base::StringPrintf;
+using base::StringToInt;
+using std::string;
+using std::vector;

[Alexei Svitkine (slow), 2014/04/30 15:25:24]

Using declarations are generally discouraged. It doesn't look like they're
adding much here, so please remove them.

Please do this in the other files too.

[bsimonnet, 2014/04/30 20:28:40]

Done.

+
+namespace metrics {
+
+SparseHistogramSample::SparseHistogramSample(const std::string& histogram_name,
+                                             int sample)
+    : MetricSample(MetricSample::SPARSE_HISTOGRAM, histogram_name),
+      sample_(sample) {}
+
+SparseHistogramSample::~SparseHistogramSample() {}
+
+string SparseHistogramSample::ToString() const {
+  return StringPrintf(
+      "sparsehistogram%c%s %d%c", '\0', name().c_str(), sample_, '\0');
+}
+
+// static
+// Read a sparse histogram from a string listing |name| and |sample| separated
+// by a space.
+SparseHistogramSample* SparseHistogramSample::ReadSparseHistogram(
+    const std::string& histogram_serialized) {
+  vector<string> parts;
+  SplitString(histogram_serialized, ' ', &parts);
+  if (parts.size() != 2) return NULL;
+  int sample;
+  if (parts[0].length() == 0 || !StringToInt(parts[1], &sample))
+    return NULL;
+
+  return new SparseHistogramSample(parts[0], sample);
+}
+
+}  // namespace metrics