Add UMA Histogram Manager to Cronet.

components/metrics/histogram_encoder_unittest.cc

+// 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_encoder.h"
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/metrics/bucket_ranges.h"
+#include "base/metrics/sample_vector.h"
+#include "base/prefs/testing_pref_service.h"
+#include "components/metrics/metrics_log.h"
+#include "components/metrics/test_metrics_service_client.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace metrics {
+
+namespace {
+
+class HistogramEncoderTest : public testing::Test {
+ public:
+  HistogramEncoderTest() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(HistogramEncoderTest);
+};
+
+}  // namespace
+
+TEST_F(HistogramEncoderTest, HistogramBucketFields) {
+  // Create buckets: 1-5, 5-7, 7-8, 8-9, 9-10, 10-11, 11-12.
+  base::BucketRanges ranges(8);
+  ranges.set_range(0, 1);
+  ranges.set_range(1, 5);
+  ranges.set_range(2, 7);
+  ranges.set_range(3, 8);
+  ranges.set_range(4, 9);
+  ranges.set_range(5, 10);
+  ranges.set_range(6, 11);
+  ranges.set_range(7, 12);
+
+  base::SampleVector samples(&ranges);
+  samples.Accumulate(3, 1);   // Bucket 1-5.
+  samples.Accumulate(6, 1);   // Bucket 5-7.
+  samples.Accumulate(8, 1);   // Bucket 8-9. (7-8 skipped)
+  samples.Accumulate(10, 1);  // Bucket 10-11. (9-10 skipped)
+  samples.Accumulate(11, 1);  // Bucket 11-12.
+
+  TestMetricsServiceClient client;
+  TestingPrefServiceSimple prefs;
+  MetricsLog log("totally bogus client ID", 137, MetricsLog::ONGOING_LOG,

[Alexei Svitkine (slow), 2014/12/10 21:50:17]

I think you should be able to omit the MetricsLog and the
TestMetricsServiceClient and TestingPrefServiceSimple from this test. Just
declare uma_proto on the stack:

ChromeUserMetricsExtension uma_proto;

+                 &client, &prefs);
+  ChromeUserMetricsExtension* uma_proto = log.uma_proto();
+  RecordHistogramDelta("Test", samples, uma_proto);
+
+  const HistogramEventProto& histogram_proto =
+      uma_proto->histogram_event(uma_proto->histogram_event_size() - 1);
+
+  // Buckets with samples: 1-5, 5-7, 8-9, 10-11, 11-12.
+  // Should become: 1-/, 5-7, /-9, 10-/, /-12.
+  ASSERT_EQ(5, histogram_proto.bucket_size());
+
+  // 1-5 becomes 1-/ (max is same as next min).
+  EXPECT_TRUE(histogram_proto.bucket(0).has_min());
+  EXPECT_FALSE(histogram_proto.bucket(0).has_max());
+  EXPECT_EQ(1, histogram_proto.bucket(0).min());
+
+  // 5-7 stays 5-7 (no optimization possible).
+  EXPECT_TRUE(histogram_proto.bucket(1).has_min());
+  EXPECT_TRUE(histogram_proto.bucket(1).has_max());
+  EXPECT_EQ(5, histogram_proto.bucket(1).min());
+  EXPECT_EQ(7, histogram_proto.bucket(1).max());
+
+  // 8-9 becomes /-9 (min is same as max - 1).
+  EXPECT_FALSE(histogram_proto.bucket(2).has_min());
+  EXPECT_TRUE(histogram_proto.bucket(2).has_max());
+  EXPECT_EQ(9, histogram_proto.bucket(2).max());
+
+  // 10-11 becomes 10-/ (both optimizations apply, omit max is prioritized).
+  EXPECT_TRUE(histogram_proto.bucket(3).has_min());
+  EXPECT_FALSE(histogram_proto.bucket(3).has_max());
+  EXPECT_EQ(10, histogram_proto.bucket(3).min());
+
+  // 11-12 becomes /-12 (last record must keep max, min is same as max - 1).
+  EXPECT_FALSE(histogram_proto.bucket(4).has_min());
+  EXPECT_TRUE(histogram_proto.bucket(4).has_max());
+  EXPECT_EQ(12, histogram_proto.bucket(4).max());
+}
+
+}  // namespace metrics