Rework UMAHistogramHelper and StatisticsDeltaReader into [Chrome]HistogramTester.

chrome/browser/search/suggestions/blacklist_store_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 "chrome/browser/search/suggestions/blacklist_store.h"
 
 #include <set>
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
-#include "base/metrics/histogram_samples.h"
-#include "base/metrics/statistics_recorder.h"
-#include "base/test/statistics_delta_reader.h"
+#include "base/test/histogram_tester.h"
 #include "chrome/browser/search/suggestions/proto/suggestions.pb.h"
 #include "components/pref_registry/testing_pref_service_syncable.h"
 #include "content/public/test/test_browser_thread_bundle.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using user_prefs::TestingPrefServiceSyncable;
 
 namespace suggestions {
 
 namespace {
@@ skipping 92 matching lines @@
   EXPECT_TRUE(blacklist_store.BlacklistUrl(GURL(kTestUrlB)));
 
   // Expect to retrieve A or B.
   EXPECT_TRUE(blacklist_store.GetFirstUrlFromBlacklist(&retrieved));
   std::string retrieved_string = retrieved.spec();
   EXPECT_TRUE(retrieved_string == std::string(kTestUrlA) ||
               retrieved_string == std::string(kTestUrlB));
 }
 
 TEST(BlacklistStoreLogTest, LogsBlacklistSize) {
+  base::HistogramTester histogram_tester;
   content::TestBrowserThreadBundle bundle;
-  base::StatisticsDeltaReader statistics_delta_reader;
 
   // Create a first store - blacklist is empty at this point.
   TestingPrefServiceSyncable prefs;
   BlacklistStore::RegisterProfilePrefs(prefs.registry());
   scoped_ptr<BlacklistStore> blacklist_store(new BlacklistStore(&prefs));
-  scoped_ptr<base::HistogramSamples> samples(
-      statistics_delta_reader.GetHistogramSamplesSinceCreation(
-          "Suggestions.LocalBlacklistSize"));
-  EXPECT_EQ(1, samples->TotalCount());
-  EXPECT_EQ(1, samples->GetCount(0));
+
+  histogram_tester.ExpectTotalCount("Suggestions.LocalBlacklistSize", 1);
+  histogram_tester.ExpectUniqueSample("Suggestions.LocalBlacklistSize", 0, 1);
 
   // Add some content to the blacklist.
   EXPECT_TRUE(blacklist_store->BlacklistUrl(GURL(kTestUrlA)));
   EXPECT_TRUE(blacklist_store->BlacklistUrl(GURL(kTestUrlB)));
 
   // Create a new BlacklistStore and verify the counts.
   blacklist_store.reset(new BlacklistStore(&prefs));
-  samples = statistics_delta_reader.GetHistogramSamplesSinceCreation(
-      "Suggestions.LocalBlacklistSize");
-  EXPECT_EQ(2, samples->TotalCount());
-  EXPECT_EQ(1, samples->GetCount(0));
-  EXPECT_EQ(1, samples->GetCount(2));
+
+  histogram_tester.ExpectTotalCount("Suggestions.LocalBlacklistSize", 2);
+  histogram_tester.ExpectBucketCount("Suggestions.LocalBlacklistSize", 0, 1);
+  histogram_tester.ExpectBucketCount("Suggestions.LocalBlacklistSize", 2, 1);
 }
 
 }  // namespace suggestions