Rework UMAHistogramHelper and StatisticsDeltaReader into [Chrome]HistogramTester.

chrome/browser/ui/cocoa/browser/password_generation_bubble_controller_unittest.mm

 // Copyright (c) 2012 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.
 
 #import "chrome/browser/ui/cocoa/browser/password_generation_bubble_controller.h"
 
 #include "base/logging.h"
 #include "base/metrics/histogram_samples.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/strings/sys_string_conversions.h"
-#include "base/test/statistics_delta_reader.h"
+#include "base/test/histogram_tester.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"
 
 const char kHistogramName[] = "PasswordGeneration.UserActions";
 
 class PasswordGenerationBubbleControllerTest : public CocoaProfileTest {
  public:
   PasswordGenerationBubbleControllerTest()
@@ skipping 52 matching lines @@
   [textfield simulateIconClick];
 
   // Make sure that the password has changed. Technically this will fail
   // about once every 1e28 times, but not something we really need to worry
   // about.
   NSString* after = [textfield stringValue];
   EXPECT_FALSE([before isEqualToString:after]);
 }
 
 TEST_F(PasswordGenerationBubbleControllerTest, UMALogging) {
-  base::StatisticsDeltaReader statistics_delta_reader;
+  base::HistogramTester histogram_tester;
   [controller() showWindow:nil];
 
   // Do nothing.
   CloseController();
 
-  scoped_ptr<base::HistogramSamples> samples(
-      statistics_delta_reader.GetHistogramSamplesSinceCreation(kHistogramName));
-  EXPECT_EQ(
-      1,
-      samples->GetCount(autofill::password_generation::IGNORE_FEATURE));
-  EXPECT_EQ(
-      0,
-      samples->GetCount(autofill::password_generation::ACCEPT_AFTER_EDITING));
-  EXPECT_EQ(
-      0,
-      samples->GetCount(
-          autofill::password_generation::ACCEPT_ORIGINAL_PASSWORD));
+  histogram_tester.ExpectUniqueSample(
+      kHistogramName, autofill::password_generation::IGNORE_FEATURE, 1);
 
   SetUpController();
 
   // Pretend like the user changed the password and accepted it.
   [controller() controlTextDidChange:nil];
   [controller() fillPassword:nil];
   CloseController();
 
-  samples =
-      statistics_delta_reader.GetHistogramSamplesSinceCreation(kHistogramName);
-  EXPECT_EQ(
-      1,
-      samples->GetCount(autofill::password_generation::IGNORE_FEATURE));
-  EXPECT_EQ(
-      1,
-      samples->GetCount(autofill::password_generation::ACCEPT_AFTER_EDITING));
-  EXPECT_EQ(
-      0,
-      samples->GetCount(
-          autofill::password_generation::ACCEPT_ORIGINAL_PASSWORD));
+  histogram_tester.ExpectBucketCount(
+      kHistogramName, autofill::password_generation::IGNORE_FEATURE, 1);
+  histogram_tester.ExpectBucketCount(
+      kHistogramName, autofill::password_generation::ACCEPT_AFTER_EDITING, 1);
+  histogram_tester.ExpectTotalCount(kHistogramName, 2);
 
   SetUpController();
 
   // Just accept the password
   [controller() fillPassword:nil];
   CloseController();
 
-  samples =
-      statistics_delta_reader.GetHistogramSamplesSinceCreation(kHistogramName);
-  EXPECT_EQ(
-      1,
-      samples->GetCount(autofill::password_generation::IGNORE_FEATURE));
-  EXPECT_EQ(
-      1,
-      samples->GetCount(autofill::password_generation::ACCEPT_AFTER_EDITING));
-  EXPECT_EQ(
-      1,
-      samples->GetCount(
-          autofill::password_generation::ACCEPT_ORIGINAL_PASSWORD));
+  histogram_tester.ExpectBucketCount(
+      kHistogramName, autofill::password_generation::IGNORE_FEATURE, 1);
+  histogram_tester.ExpectBucketCount(
+      kHistogramName, autofill::password_generation::ACCEPT_AFTER_EDITING, 1);
+  histogram_tester.ExpectBucketCount(
+      kHistogramName,
+      autofill::password_generation::ACCEPT_ORIGINAL_PASSWORD,
+      1);
+  histogram_tester.ExpectTotalCount(kHistogramName, 3);
 }