[Metrics] Don't require clients of StatisticsDeltaReader to call StatisticsRecorder::Initialize().

BUG=none
TEST=none
R=asvitkine@chromium.org
TBR=willchan@chromium.org

Review URL: https://codereview.chromium.org/184203002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256495 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 9 insertions, 23 deletions

diff --git a/base/test/statistics_delta_reader.cc b/base/test/statistics_delta_reader.cc
index 9e77b8b..93ce1ad 100644
--- a/base/test/statistics_delta_reader.cc
+++ b/base/test/statistics_delta_reader.cc
@@ -5,12 +5,15 @@
 #include "base/test/statistics_delta_reader.h"
 
 #include "base/metrics/histogram.h"
+#include "base/metrics/histogram_samples.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/stl_util.h"
 
 namespace base {
 
 StatisticsDeltaReader::StatisticsDeltaReader() {
+  StatisticsRecorder::Initialize();  // Safe to call multiple times.
+
   // Record any histogram data that exists when the object is created so it can
   // be subtracted later.
   StatisticsRecorder::Histograms histograms;
diff --git a/base/test/statistics_delta_reader.h b/base/test/statistics_delta_reader.h
index c4e4e99..4921d61d 100644
--- a/base/test/statistics_delta_reader.h
+++ b/base/test/statistics_delta_reader.h
@@ -10,13 +10,13 @@
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/metrics/histogram_samples.h"
 
 namespace base {
 
+class HistogramSamples;
+
 // This class acts as a differential reader for histogram samples, enabling
 // tests to check that metrics were recorded as they should be.
-// Before using this class, StatisticsRecoder must be initialized.
 class StatisticsDeltaReader {
  public:
   StatisticsDeltaReader();
diff --git a/base/test/statistics_delta_reader_unittest.cc b/base/test/statistics_delta_reader_unittest.cc
index acf8d5a..55180d1 100644
--- a/base/test/statistics_delta_reader_unittest.cc
+++ b/base/test/statistics_delta_reader_unittest.cc
@@ -2,32 +2,16 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "base/test/statistics_delta_reader.h"
+
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/histogram_samples.h"
-#include "base/metrics/statistics_recorder.h"
-#include "base/test/statistics_delta_reader.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
-class StatisticsDeltaReaderTest : public testing::Test {
- protected:
-  virtual void SetUp() OVERRIDE {
-    // Each test will have a clean state (no Histogram / BucketRanges
-    // registered).
-    statistics_recorder_ = new StatisticsRecorder();
-  }
-
-  virtual void TearDown() OVERRIDE {
-    delete statistics_recorder_;
-    statistics_recorder_ = NULL;
-  }
-
-  StatisticsRecorder* statistics_recorder_;
-};
-
-TEST_F(StatisticsDeltaReaderTest, Scope) {
+TEST(StatisticsDeltaReaderTest, Scope) {
   // Record a histogram before the creation of the recorder.
   UMA_HISTOGRAM_BOOLEAN("Test", true);
 
@@ -36,8 +20,7 @@ TEST_F(StatisticsDeltaReaderTest, Scope) {
   // Verify that no histogram is recorded.
   scoped_ptr<HistogramSamples> samples(
       reader.GetHistogramSamplesSinceCreation("Test"));
-  EXPECT_TRUE(samples);
-  EXPECT_EQ(0, samples->TotalCount());
+  EXPECT_FALSE(samples);
 
   // Record a histogram after the creation of the recorder.
   UMA_HISTOGRAM_BOOLEAN("Test", true);