Rework UMAHistogramHelper and StatisticsDeltaReader into [Chrome]HistogramTester.

chrome/browser/ui/views/profiles/profile_chooser_view_browsertest.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/ui/views/profiles/profile_chooser_view.h"
 
 #include "base/command_line.h"
 #include "base/path_service.h"
 #include "base/prefs/pref_service.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/test/histogram_tester.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chrome/browser/profiles/profile_metrics.h"
 #include "chrome/browser/profiles/profiles_state.h"
 #include "chrome/browser/ui/browser_dialogs.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/views/frame/browser_view.h"
 #include "chrome/browser/ui/views/profiles/avatar_menu_button.h"
 #include "chrome/browser/ui/views/profiles/new_avatar_button.h"
 #include "chrome/browser/ui/views/profiles/user_manager_view.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/test_switches.h"
 #include "chrome/test/base/testing_browser_process.h"
 #include "chrome/test/base/testing_profile_manager.h"
-#include "chrome/test/base/uma_histogram_helper.h"
 #include "components/signin/core/common/profile_management_switches.h"
 #include "content/public/test/test_utils.h"
 #include "grit/generated_resources.h"
 #include "ui/views/controls/button/label_button.h"
 
 class ProfileChooserViewBrowserTest : public InProcessBrowserTest {
  public:
   ProfileChooserViewBrowserTest();
   virtual ~ProfileChooserViewBrowserTest();
 
@@ skipping 40 matching lines @@
 // This test doesn't make sense for ChromeOS since it has a different
 // multi-profiles menu in the system tray instead.
 //
 // Mobile platforms are also excluded due to a lack of avatar menu.
 #define MAYBE_ViewProfileUMA DISABLED_ViewProfileUMA
 #else
 #define MAYBE_ViewProfileUMA ViewProfileUMA
 #endif
 
 IN_PROC_BROWSER_TEST_F(ProfileChooserViewBrowserTest, MAYBE_ViewProfileUMA) {
-  UMAHistogramHelper histograms;
+  base::HistogramTester histograms;
   // If multiprofile mode is not enabled, you can't switch between profiles.
   if (!profiles::IsMultipleProfilesEnabled())
     return;
 
   Profile* profile = browser()->profile();
   profile->GetPrefs()->SetInteger(prefs::kProfileAvatarTutorialShown, 0);
 
   ASSERT_NO_FATAL_FAILURE(OpenProfileChooserView());
 
-  histograms.Fetch();

[msw, 2014/07/18 17:30:25]

Were the NaCl tests the only ones that actually required this synchronization?
You removed this and many other Fetch() calls without adding
FetchHistogramsFromChildProcesses() calls (except for NaCl).

[Ilya Sherman, 2014/07/18 17:32:00]

Indeed, the NaCl tests were the only ones that actually needed to fetch
histograms data from child processes.

   histograms.ExpectUniqueSample("Profile.UpgradeEnrollment",
       ProfileMetrics::PROFILE_ENROLLMENT_SHOW_PREVIEW_PROMO, 1);
 }