Revert 242121 "Reland "Add a HistogramRecorder class and use cas..."

As per request from lpromero, reverting since it might be failing a
test - see

http://build.chromium.org/p/chromium.memory.fyi/builders/Windows%20Tests%20%28tsan%29/builds/17153/steps/memory%20test%3A%20base_unittests/logs/stdio

[ RUN      ] HistogramTest.BasicTest
[3824:2780:1220/111332:4747750:FATAL:statistics_recorder.cc(270)] Check failed: !histograms_.

TBR=lpromero@chromium.org

> Reland "Add a HistogramRecorder class and use cases."
> 
> This CL adds a utility class to streamline the task of testing that metrics have been updated as expected. Specifically, the HistogramRecorder class allows a client to obtain the differential value of a given histogram in the interval since the given HistogramRecorder instance was created.
> 
> This reverts commit b957026f43ef9464a8cdd5a240867c807b2281da.
> 
> BUG=232414
> TBR=rsleevi, mark, groby, thakis
> 
> Review URL: https://codereview.chromium.org/19866004

TBR=lpromero@chromium.org

Review URL: https://codereview.chromium.org/120273002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242176 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 162 insertions, 205 deletions

diff --git a/base/base.gyp b/base/base.gyp
index 1bd8e53..1c2e931 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -640,7 +640,6 @@
         'template_util_unittest.cc',
         'test/expectations/expectation_unittest.cc',
         'test/expectations/parser_unittest.cc',
-        'test/histogram_recorder_unittest.cc',
         'test/test_reg_util_win_unittest.cc',
         'test/trace_event_analyzer_unittest.cc',
         'threading/non_thread_safe_unittest.cc',
@@ -907,8 +906,6 @@
         'test/expectations/parser.h',
         'test/gtest_xml_util.cc',
         'test/gtest_xml_util.h',
-        'test/histogram_recorder.cc',
-        'test/histogram_recorder.h',
         'test/launcher/test_launcher.cc',
         'test/launcher/test_launcher.h',
         'test/launcher/test_result.cc',
diff --git a/base/metrics/statistics_recorder.h b/base/metrics/statistics_recorder.h
index 9cf1de7..0716e80 100644
--- a/base/metrics/statistics_recorder.h
+++ b/base/metrics/statistics_recorder.h
@@ -70,9 +70,9 @@ class BASE_EXPORT StatisticsRecorder {
   static HistogramBase* FindHistogram(const std::string& name);
 
   // GetSnapshot copies some of the pointers to registered histograms into the
-  // caller supplied vector (Histograms). Only histograms which have |query| as
-  // a substring are copied (an empty string will process all registered
-  // histograms).
+  // caller supplied vector (Histograms).  Only histograms with names matching
+  // query are returned. The query must be a substring of histogram name for its
+  // pointer to be copied.
   static void GetSnapshot(const std::string& query, Histograms* snapshot);
 
  private:
diff --git a/base/test/histogram_recorder.cc b/base/test/histogram_recorder.cc
deleted file mode 100644
index ee852f7..0000000
--- a/base/test/histogram_recorder.cc
+++ /dev/null
@@ -1,52 +0,0 @@
-// Copyright 2013 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 "base/test/histogram_recorder.h"
-
-#include "base/metrics/histogram.h"
-#include "base/metrics/statistics_recorder.h"
-#include "base/stl_util.h"
-
-namespace base {
-
-// static
-void HistogramRecorder::Initialize() {
-  // Ensure that StatisticsRecorder is initialized.
-  StatisticsRecorder::Initialize();
-}
-
-HistogramRecorder::HistogramRecorder() {
-  // Record any histogram data that exists when the object is created so it can
-  // be subtracted later.
-  StatisticsRecorder::Histograms histograms;
-  StatisticsRecorder::GetSnapshot("", &histograms);
-  for (size_t i = 0; i < histograms.size(); i++) {
-    original_samples_[histograms[i]->histogram_name()] =
-        histograms[i]->SnapshotSamples().release();
-  }
-}
-
-HistogramRecorder::~HistogramRecorder() {
-  STLDeleteValues(&original_samples_);
-}
-
-// static
-bool HistogramRecorder::IsActive() {
-  return StatisticsRecorder::IsActive();
-}
-
-scoped_ptr<HistogramSamples>
-    HistogramRecorder::GetHistogramSamplesSinceCreation(
-        const std::string& histogram_name) {
-  HistogramBase* histogram = StatisticsRecorder::FindHistogram(histogram_name);
-  if (!histogram)
-    return scoped_ptr<HistogramSamples>();
-  scoped_ptr<HistogramSamples> named_samples(histogram->SnapshotSamples());
-  HistogramSamples* named_original_samples = original_samples_[histogram_name];
-  if (named_original_samples)
-    named_samples->Subtract(*named_original_samples);
-  return named_samples.Pass();
-}
-
-}  // namespace base
diff --git a/base/test/histogram_recorder.h b/base/test/histogram_recorder.h
deleted file mode 100644
index f867b1e..0000000
--- a/base/test/histogram_recorder.h
+++ /dev/null
@@ -1,44 +0,0 @@
-// Copyright 2013 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.
-
-#ifndef BASE_TEST_HISTOGRAM_RECORDER_H_
-#define BASE_TEST_HISTOGRAM_RECORDER_H_
-
-#include <map>
-
-#include "base/basictypes.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/metrics/histogram_samples.h"
-
-namespace base {
-
-// This class acts as a differential reader for histogram samples, enabling
-// tests to check that metrics were recorded as they should be.
-class HistogramRecorder {
- public:
-  // Initializes the HistogramRecorder system.
-  static void Initialize();
-  HistogramRecorder();
-  virtual ~HistogramRecorder();
-
-  // Returns whether the HistogramRecorder has been initialized.
-  static bool IsActive();
-
-  // Returns the histogram data accumulated since this instance was created.
-  // Returns NULL if no samples are available.
-  scoped_ptr<HistogramSamples> GetHistogramSamplesSinceCreation(
-      const std::string& histogram_name);
-
- private:
-  // Used to determine the histogram changes made during this instance's
-  // lifecycle. This isntance takes ownership of the samples, which are deleted
-  // when the instance is destroyed.
-  std::map<std::string, HistogramSamples*> original_samples_;
-
-  DISALLOW_COPY_AND_ASSIGN(HistogramRecorder);
-};
-
-}  // namespace base
-
-#endif  // BASE_TEST_HISTOGRAM_RECORDER_H_
diff --git a/base/test/histogram_recorder_unittest.cc b/base/test/histogram_recorder_unittest.cc
deleted file mode 100644
index f4cdf49..0000000
--- a/base/test/histogram_recorder_unittest.cc
+++ /dev/null
@@ -1,41 +0,0 @@
-// Copyright 2013 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 "base/memory/scoped_ptr.h"
-#include "base/metrics/histogram.h"
-#include "base/metrics/histogram_samples.h"
-#include "base/test/histogram_recorder.h"
-#include "testing/gtest/include/gtest/gtest.h"
-
-namespace base {
-
-class HistogramRecorderTest : public testing::Test {
- public:
-  static void SetUpTestCase() {
-    HistogramRecorder::Initialize();
-  }
-};
-
-TEST_F(HistogramRecorderTest, Scope) {
-  // Record a histogram before the creation of the recorder.
-  UMA_HISTOGRAM_BOOLEAN("Test", true);
-
-  HistogramRecorder recorder;
-
-  // Verify that no histogram is recorded.
-  scoped_ptr<HistogramSamples> samples(
-      recorder.GetHistogramSamplesSinceCreation("Test"));
-  EXPECT_TRUE(samples);
-  EXPECT_EQ(0, samples->TotalCount());
-
-  // Record a histogram after the creation of the recorder.
-  UMA_HISTOGRAM_BOOLEAN("Test", true);
-
-  // Verify that one histogram is recorded.
-  samples = recorder.GetHistogramSamplesSinceCreation("Test");
-  EXPECT_TRUE(samples);
-  EXPECT_EQ(1, samples->TotalCount());
-}
-
-}  // namespace base
diff --git a/chrome/browser/spellchecker/spellcheck_host_metrics_unittest.cc b/chrome/browser/spellchecker/spellcheck_host_metrics_unittest.cc
index f702723..ab7348a 100644
--- a/chrome/browser/spellchecker/spellcheck_host_metrics_unittest.cc
+++ b/chrome/browser/spellchecker/spellcheck_host_metrics_unittest.cc
@@ -7,9 +7,10 @@
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
+#include "base/metrics/histogram.h"
 #include "base/metrics/histogram_samples.h"
+#include "base/metrics/statistics_recorder.h"
 #include "base/strings/utf_string_conversions.h"
-#include "base/test/histogram_recorder.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 #if defined(OS_WIN)
@@ -17,51 +18,55 @@
 #include "base/win/windows_version.h"
 #endif
 
+using base::HistogramBase;
+using base::HistogramSamples;
+using base::StatisticsRecorder;
+
 class SpellcheckHostMetricsTest : public testing::Test {
  public:
   SpellcheckHostMetricsTest() : loop_(base::MessageLoop::TYPE_DEFAULT) {
   }
 
-  static void SetUpTestCase() {
-    base::HistogramRecorder::Initialize();
-  }
-
   virtual void SetUp() OVERRIDE {
-    ResetHistogramRecorder();
+    base::StatisticsRecorder::Initialize();
     metrics_.reset(new SpellCheckHostMetrics);
   }
 
-  void ResetHistogramRecorder() {
-    histogram_recorder_.reset(new base::HistogramRecorder());
-  }
-
   SpellCheckHostMetrics* metrics() { return metrics_.get(); }
   void RecordWordCountsForTesting() { metrics_->RecordWordCounts(); }
 
- protected:
-  scoped_ptr<base::HistogramRecorder> histogram_recorder_;
-
  private:
   base::MessageLoop loop_;
   scoped_ptr<SpellCheckHostMetrics> metrics_;
 };
 
 TEST_F(SpellcheckHostMetricsTest, RecordEnabledStats) {
-  const char kMetricName[] = "SpellCheck.Enabled";
+  scoped_ptr<HistogramSamples> baseline;
+  HistogramBase* histogram =
+      StatisticsRecorder::FindHistogram("SpellCheck.Enabled");
+  if (histogram)
+    baseline = histogram->SnapshotSamples();
 
   metrics()->RecordEnabledStats(false);
 
-  scoped_ptr<base::HistogramSamples> samples(
-      histogram_recorder_->GetHistogramSamplesSinceCreation(kMetricName));
+  histogram =
+      StatisticsRecorder::FindHistogram("SpellCheck.Enabled");
+  ASSERT_TRUE(histogram != NULL);
+  scoped_ptr<HistogramSamples> samples(histogram->SnapshotSamples());
+  if (baseline.get())
+    samples->Subtract(*baseline);
   EXPECT_EQ(1, samples->GetCount(0));
   EXPECT_EQ(0, samples->GetCount(1));
 
-  ResetHistogramRecorder();
+  baseline.reset(samples.release());
 
   metrics()->RecordEnabledStats(true);
 
-  samples =
-      histogram_recorder_->GetHistogramSamplesSinceCreation(kMetricName);
+  histogram =
+      StatisticsRecorder::FindHistogram("SpellCheck.Enabled");
+  ASSERT_TRUE(histogram != NULL);
+  samples = histogram->SnapshotSamples();
+  samples->Subtract(*baseline);
   EXPECT_EQ(0, samples->GetCount(0));
   EXPECT_EQ(1, samples->GetCount(1));
 }
@@ -76,16 +81,21 @@ TEST_F(SpellcheckHostMetricsTest, CustomWordStats) {
 
   // Determine if test failures are due the statistics recorder not being
   // available or because the histogram just isn't there: crbug.com/230534.
-  EXPECT_TRUE(base::HistogramRecorder::IsActive());
+  EXPECT_TRUE(StatisticsRecorder::IsActive());
 
-  ResetHistogramRecorder();
+  HistogramBase* histogram =
+      StatisticsRecorder::FindHistogram("SpellCheck.CustomWords");
+  ASSERT_TRUE(histogram != NULL);
+  scoped_ptr<HistogramSamples> baseline = histogram->SnapshotSamples();
 
   SpellCheckHostMetrics::RecordCustomWordCountStats(23);
+  histogram =
+      StatisticsRecorder::FindHistogram("SpellCheck.CustomWords");
+  ASSERT_TRUE(histogram != NULL);
+  scoped_ptr<HistogramSamples> samples = histogram->SnapshotSamples();
 
-  scoped_ptr<base::HistogramSamples> samples(
-      histogram_recorder_->GetHistogramSamplesSinceCreation(
-          "SpellCheck.CustomWords"));
-  EXPECT_EQ(23, samples->sum());
+  samples->Subtract(*baseline);
+  EXPECT_EQ(23,samples->sum());
 }
 
 TEST_F(SpellcheckHostMetricsTest, RecordWordCountsDiscardsDuplicates) {
@@ -103,37 +113,59 @@ TEST_F(SpellcheckHostMetricsTest, RecordWordCountsDiscardsDuplicates) {
   metrics()->RecordCheckedWordStats(ASCIIToUTF16("test"), false);
   RecordWordCountsForTesting();
 
-  // Restart the recorder.
-  ResetHistogramRecorder();
+  // Get baselines for all affected histograms.
+  scoped_ptr<HistogramSamples> baselines[arraysize(histogramName)];
+  for (size_t i = 0; i < arraysize(histogramName); ++i) {
+    HistogramBase* histogram =
+        StatisticsRecorder::FindHistogram(histogramName[i]);
+    if (histogram)
+      baselines[i] = histogram->SnapshotSamples();
+  }
 
   // Nothing changed, so this invocation should not affect any histograms.
   RecordWordCountsForTesting();
 
   // Get samples for all affected histograms.
-  scoped_ptr<base::HistogramSamples> samples;
+  scoped_ptr<HistogramSamples> samples[arraysize(histogramName)];
   for (size_t i = 0; i < arraysize(histogramName); ++i) {
-    samples = histogram_recorder_->GetHistogramSamplesSinceCreation(
-        histogramName[i]);
-    EXPECT_EQ(0, samples->TotalCount());
+    HistogramBase* histogram =
+        StatisticsRecorder::FindHistogram(histogramName[i]);
+    ASSERT_TRUE(histogram != NULL);
+    samples[i] = histogram->SnapshotSamples();
+    if (baselines[i].get())
+      samples[i]->Subtract(*baselines[i]);
+
+    EXPECT_EQ(0, samples[i]->TotalCount());
   }
 }
 
 TEST_F(SpellcheckHostMetricsTest, RecordSpellingServiceStats) {
   const char kMetricName[] = "SpellCheck.SpellingService.Enabled";
+  scoped_ptr<HistogramSamples> baseline;
+  HistogramBase* histogram = StatisticsRecorder::FindHistogram(kMetricName);
+  if (histogram)
+    baseline = histogram->SnapshotSamples();
 
   metrics()->RecordSpellingServiceStats(false);
 
-  scoped_ptr<base::HistogramSamples> samples(
-      histogram_recorder_->GetHistogramSamplesSinceCreation(kMetricName));
+  histogram =
+      StatisticsRecorder::FindHistogram(kMetricName);
+  ASSERT_TRUE(histogram != NULL);
+  scoped_ptr<HistogramSamples> samples(histogram->SnapshotSamples());
+  if (baseline.get())
+    samples->Subtract(*baseline);
   EXPECT_EQ(1, samples->GetCount(0));
   EXPECT_EQ(0, samples->GetCount(1));
 
-  ResetHistogramRecorder();
+  baseline.reset(samples.release());
 
   metrics()->RecordSpellingServiceStats(true);
 
-  samples =
-      histogram_recorder_->GetHistogramSamplesSinceCreation(kMetricName);
+  histogram =
+      StatisticsRecorder::FindHistogram(kMetricName);
+  ASSERT_TRUE(histogram != NULL);
+  samples = histogram->SnapshotSamples();
+  samples->Subtract(*baseline);
   EXPECT_EQ(0, samples->GetCount(0));
   EXPECT_EQ(1, samples->GetCount(1));
 }
diff --git a/chrome/browser/ui/cocoa/browser/password_generation_bubble_controller_unittest.mm b/chrome/browser/ui/cocoa/browser/password_generation_bubble_controller_unittest.mm
index b9af977..c3211714 100644
--- a/chrome/browser/ui/cocoa/browser/password_generation_bubble_controller_unittest.mm
+++ b/chrome/browser/ui/cocoa/browser/password_generation_bubble_controller_unittest.mm
@@ -5,14 +5,19 @@
 #import "chrome/browser/ui/cocoa/browser/password_generation_bubble_controller.h"
 
 #include "base/logging.h"
+#include "base/metrics/histogram.h"
 #include "base/metrics/histogram_samples.h"
+#include "base/metrics/statistics_recorder.h"
 #include "base/strings/sys_string_conversions.h"
-#include "base/test/histogram_recorder.h"
 #include "chrome/browser/ui/cocoa/cocoa_profile_test.h"
 #include "components/autofill/core/browser/password_generator.h"
 #include "components/autofill/core/common/password_form.h"
 #include "testing/gtest_mac.h"
 
+using base::HistogramBase;
+using base::HistogramSamples;
+using base::StatisticsRecorder;
+
 const char kHistogramName[] = "PasswordGeneration.UserActions";
 
 class PasswordGenerationBubbleControllerTest : public CocoaProfileTest {
@@ -21,7 +26,7 @@ class PasswordGenerationBubbleControllerTest : public CocoaProfileTest {
       : controller_(nil) {}
 
   static void SetUpTestCase() {
-    base::HistogramRecorder::Initialize();
+    StatisticsRecorder::Initialize();
   }
 
   virtual void SetUp() {
@@ -29,7 +34,10 @@ class PasswordGenerationBubbleControllerTest : public CocoaProfileTest {
 
     generator_.reset(new autofill::PasswordGenerator(20));
 
-    histogram_recorder_.reset(new base::HistogramRecorder());
+    HistogramBase* histogram =
+        StatisticsRecorder::FindHistogram(kHistogramName);
+    if (histogram)
+      original_ = histogram->SnapshotSamples();
 
     SetUpController();
   }
@@ -57,16 +65,26 @@ class PasswordGenerationBubbleControllerTest : public CocoaProfileTest {
     controller_ = nil;
   }
 
-  scoped_ptr<base::HistogramSamples> GetHistogramSamples() {
-    return histogram_recorder_->GetHistogramSamplesSinceCreation(
-        kHistogramName).Pass();
+  HistogramSamples* GetHistogramSamples() {
+    HistogramBase* histogram =
+        StatisticsRecorder::FindHistogram(kHistogramName);
+    if (histogram) {
+      current_ = histogram->SnapshotSamples();
+      if (original_.get())
+        current_->Subtract(*original_.get());
+    }
+    return current_.get();
   }
 
  protected:
   // Weak.
   PasswordGenerationBubbleController* controller_;
 
-  scoped_ptr<base::HistogramRecorder> histogram_recorder_;
+  // Used to determine the histogram changes made just for this specific
+  // test run.
+  scoped_ptr<HistogramSamples> original_;
+
+  scoped_ptr<HistogramSamples> current_;
 
   scoped_ptr<autofill::PasswordGenerator> generator_;
 };
@@ -94,7 +112,7 @@ TEST_F(PasswordGenerationBubbleControllerTest, UMALogging) {
   // Do nothing.
   CloseController();
 
-  scoped_ptr<base::HistogramSamples> samples(GetHistogramSamples());
+  HistogramSamples* samples = GetHistogramSamples();
   EXPECT_EQ(
       1,
       samples->GetCount(autofill::password_generation::IGNORE_FEATURE));
@@ -142,4 +160,5 @@ TEST_F(PasswordGenerationBubbleControllerTest, UMALogging) {
       1,
       samples->GetCount(
           autofill::password_generation::ACCEPT_ORIGINAL_PASSWORD));
+
 }
diff --git a/net/url_request/url_request_throttler_unittest.cc b/net/url_request/url_request_throttler_unittest.cc
index 52b3a0a..b964b10 100644
--- a/net/url_request/url_request_throttler_unittest.cc
+++ b/net/url_request/url_request_throttler_unittest.cc
@@ -5,12 +5,13 @@
 #include "net/url_request/url_request_throttler_manager.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/pickle.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
-#include "base/test/histogram_recorder.h"
 #include "base/time/time.h"
 #include "net/base/load_flags.h"
 #include "net/base/request_priority.h"
@@ -28,7 +29,10 @@ namespace net {
 
 namespace {
 
-const char kRequestThrottledHistogramName[] = "Throttling.RequestThrottled";
+using base::Histogram;
+using base::HistogramBase;
+using base::HistogramSamples;
+using base::StatisticsRecorder;
 
 class MockURLRequestThrottlerEntry : public URLRequestThrottlerEntry {
  public:
@@ -172,22 +176,32 @@ class URLRequestThrottlerEntryTest : public testing::Test {
   URLRequestThrottlerEntryTest()
       : request_(GURL(), DEFAULT_PRIORITY, NULL, &context_) {}
 
-  static void SetUpTestCase() {
-    base::HistogramRecorder::Initialize();
-  }
-
   virtual void SetUp();
+  virtual void TearDown();
+
+  // After calling this function, histogram snapshots in |samples_| contain
+  // only the delta caused by the test case currently running.
+  void CalculateHistogramDeltas();
 
   TimeTicks now_;
   MockURLRequestThrottlerManager manager_;  // Dummy object, not used.
   scoped_refptr<MockURLRequestThrottlerEntry> entry_;
 
-  scoped_ptr<base::HistogramRecorder> histogram_recorder_;
+  std::map<std::string, HistogramSamples*> original_samples_;
+  std::map<std::string, HistogramSamples*> samples_;
 
   TestURLRequestContext context_;
   TestURLRequest request_;
 };
 
+// List of all histograms we care about in these unit tests.
+const char* kHistogramNames[] = {
+  "Throttling.FailureCountAtSuccess",
+  "Throttling.PerceivedDowntime",
+  "Throttling.RequestThrottled",
+  "Throttling.SiteOptedOut",
+};
+
 void URLRequestThrottlerEntryTest::SetUp() {
   request_.SetLoadFlags(0);
 
@@ -195,7 +209,43 @@ void URLRequestThrottlerEntryTest::SetUp() {
   entry_ = new MockURLRequestThrottlerEntry(&manager_);
   entry_->ResetToBlank(now_);
 
-  histogram_recorder_.reset(new base::HistogramRecorder());
+  for (size_t i = 0; i < arraysize(kHistogramNames); ++i) {
+    // Must retrieve original samples for each histogram for comparison
+    // as other tests may affect them.
+    const char* name = kHistogramNames[i];
+    HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
+    if (histogram) {
+      original_samples_[name] = histogram->SnapshotSamples().release();
+    } else {
+      original_samples_[name] = NULL;
+    }
+  }
+}
+
+void URLRequestThrottlerEntryTest::TearDown() {
+  STLDeleteValues(&original_samples_);
+  STLDeleteValues(&samples_);
+}
+
+void URLRequestThrottlerEntryTest::CalculateHistogramDeltas() {
+  for (size_t i = 0; i < arraysize(kHistogramNames); ++i) {
+    const char* name = kHistogramNames[i];
+    HistogramSamples* original = original_samples_[name];
+
+    HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
+    if (histogram) {
+      ASSERT_EQ(HistogramBase::kUmaTargetedHistogramFlag, histogram->flags());
+
+      scoped_ptr<HistogramSamples> samples(histogram->SnapshotSamples());
+      if (original)
+        samples->Subtract(*original);
+      samples_[name] = samples.release();
+    }
+  }
+
+  // Ensure we don't accidentally use the originals in our tests.
+  STLDeleteValues(&original_samples_);
+  original_samples_.clear();
 }
 
 std::ostream& operator<<(std::ostream& out, const base::TimeTicks& time) {
@@ -223,11 +273,9 @@ TEST_F(URLRequestThrottlerEntryTest, InterfaceDuringExponentialBackoff) {
   request_.SetLoadFlags(LOAD_MAYBE_USER_GESTURE);
   EXPECT_FALSE(entry_->ShouldRejectRequest(request_));
 
-  scoped_ptr<base::HistogramSamples> samples(
-      histogram_recorder_->GetHistogramSamplesSinceCreation(
-          kRequestThrottledHistogramName));
-  ASSERT_EQ(1, samples->GetCount(0));
-  ASSERT_EQ(1, samples->GetCount(1));
+  CalculateHistogramDeltas();
+  ASSERT_EQ(1, samples_["Throttling.RequestThrottled"]->GetCount(0));
+  ASSERT_EQ(1, samples_["Throttling.RequestThrottled"]->GetCount(1));
 }
 
 TEST_F(URLRequestThrottlerEntryTest, InterfaceNotDuringExponentialBackoff) {
@@ -237,11 +285,9 @@ TEST_F(URLRequestThrottlerEntryTest, InterfaceNotDuringExponentialBackoff) {
       entry_->fake_time_now_ - TimeDelta::FromMilliseconds(1));
   EXPECT_FALSE(entry_->ShouldRejectRequest(request_));
 
-  scoped_ptr<base::HistogramSamples> samples(
-      histogram_recorder_->GetHistogramSamplesSinceCreation(
-          kRequestThrottledHistogramName));
-  ASSERT_EQ(2, samples->GetCount(0));
-  ASSERT_EQ(0, samples->GetCount(1));
+  CalculateHistogramDeltas();
+  ASSERT_EQ(2, samples_["Throttling.RequestThrottled"]->GetCount(0));
+  ASSERT_EQ(0, samples_["Throttling.RequestThrottled"]->GetCount(1));
 }
 
 TEST_F(URLRequestThrottlerEntryTest, InterfaceUpdateFailure) {