Rework UMAHistogramHelper and StatisticsDeltaReader into [Chrome]HistogramTester.

chrome/browser/ui/views/passwords/manage_passwords_view_test.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/passwords/manage_passwords_view_test.h"
 
-#include "base/test/statistics_delta_reader.h"
+#include "base/test/histogram_tester.h"

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

nit: you don't need to explicitly include this here since it's in the header.

[Mike Lerman, 2014/07/18 18:23:58]

Done.

 #include "chrome/app/chrome_command_ids.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_command_controller.h"
 #include "chrome/browser/ui/passwords/manage_passwords_icon.h"
 #include "chrome/browser/ui/passwords/manage_passwords_ui_controller_mock.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/views/frame/browser_view.h"
 #include "chrome/browser/ui/views/passwords/manage_passwords_bubble_view.h"
 #include "chrome/browser/ui/views/passwords/manage_passwords_icon_view.h"
 #include "chrome/browser/ui/views/toolbar/toolbar_view.h"
@@ skipping 65 matching lines @@
   autofill::PasswordFormMap map;
   map[kTestUsername] = test_form();
   controller()->OnBlacklistBlockedAutofill(map);
   controller()->UpdateIconAndBubbleState(view());
 }
 
 base::HistogramSamples* ManagePasswordsViewTest::GetSamples(
     const char* histogram) {
   // Ensure that everything has been properly recorded before pulling samples.
   content::RunAllPendingInMessageLoop();
-  return statistics_reader_.GetHistogramSamplesSinceCreation(
-      histogram).release();
+  return histogram_tester_.GetHistogramSamplesSinceCreation(histogram)

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

nit: or make this function-local, not a class member, since it's only used here.

[Mike Lerman, 2014/07/18 18:23:58]

The timing of the execution of the constructor is important here, as it gathers
snapshot data as a baseline for comparison. If I remove this from being a class
member, I would instead have to create it in at the beginning of each of the
test methods that calls GetSamples(), and then pass in that HistogramTester to
this object. The current implementation seems cleaner.

+      .release();
 }