Add UMA Histogram Manager to Cronet.

components/metrics/histogram_manager_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_manager.h"
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace metrics {
+
+// TODO(mef): crbug.com/441441. Move components/metrics/histogram_manager.*
+// files into components/android/cronet.
+TEST(HistogramManager, HistogramBucketFields) {
+  // kNoFlags filter should record all histograms.
+  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 2);
+
+  std::vector<uint8> data;
+  EXPECT_TRUE(HistogramManager::GetInstance()->GetDeltas(&data));
+  EXPECT_LT(0u, data.size());

[Alexei Svitkine (slow), 2014/12/12 16:57:00]

I thought I mention this in a previous comment, but I think this should be

EXPECT_FALSE(data.empty());

[ramant (doing other things), 2014/12/12 19:01:26]

Sorry missed the above change.

Done.

+  ChromeUserMetricsExtension uma_proto;
+  EXPECT_TRUE(uma_proto.ParseFromArray(
+      reinterpret_cast<const char*>(&data[0]), data.size()));
+  EXPECT_LT(0u, data.size());
+
+  const HistogramEventProto& histogram_proto =
+      uma_proto.histogram_event(uma_proto.histogram_event_size() - 1);
+  ASSERT_EQ(1, histogram_proto.bucket_size());

[Alexei Svitkine (slow), 2014/12/12 16:57:00]

I got a test failure here:


[----------] 1 test from HistogramManager
[ RUN      ] HistogramManager.HistogramBucketFields
../../components/metrics/histogram_manager_unittest.cc:30: Failure
Value of: histogram_proto.bucket_size()
  Actual: 6
Expected: 1
[  FAILED  ] HistogramManager.HistogramBucketFields (4 ms)
[----------] 1 test from HistogramManager (4 ms total)



When running with the following command-line locally:

 ./out/Debug/components_unittests --single-process-tests

I think this is flaky because it may pick up other histograms that were logged
before the test has run. I suggest adding an initial GetDeltas() call to capture
those at the start of the test, so later GetDeltas() calls won't pick them up.

[ramant (doing other things), 2014/12/12 19:01:26]

Awesome. Many many thanks for the above idea. Removes the potential flakiness.

Done.

+  EXPECT_LE(0, histogram_proto.bucket(0).min());
+  EXPECT_LE(2, histogram_proto.bucket(0).max());
+  EXPECT_EQ(1, histogram_proto.bucket(0).count());
+
+  UMA_STABILITY_HISTOGRAM_ENUMERATION("UmaStabilityHistogram", 2, 3);
+  std::vector<uint8> data2;
+  EXPECT_TRUE(HistogramManager::GetInstance()->GetDeltas(&data2));
+  EXPECT_LT(0u, data2.size());
+  ChromeUserMetricsExtension uma_proto2;
+  EXPECT_TRUE(uma_proto2.ParseFromArray(
+      reinterpret_cast<const char*>(&data2[0]), data2.size()));
+  EXPECT_LT(0u, data2.size());
+
+  const HistogramEventProto& histogram_proto2 =
+      uma_proto2.histogram_event(uma_proto2.histogram_event_size() - 1);
+  ASSERT_EQ(1, histogram_proto2.bucket_size());
+  EXPECT_LE(0, histogram_proto2.bucket(0).min());
+  EXPECT_LE(3, histogram_proto2.bucket(0).max());
+  EXPECT_EQ(1, histogram_proto2.bucket(0).count());
+}
+
+}  // namespace metrics