Rework UMAHistogramHelper and StatisticsDeltaReader into [Chrome]HistogramTester.

chrome/test/base/uma_histogram_helper.cc

-// 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.
-
-#include "chrome/test/base/uma_histogram_helper.h"
-
-#include "base/bind.h"
-#include "base/metrics/statistics_recorder.h"
-#include "base/test/test_timeouts.h"
-#include "chrome/test/base/ui_test_utils.h"
-#include "content/public/browser/histogram_fetcher.h"
-
-UMAHistogramHelper::UMAHistogramHelper() {
-  base::StatisticsRecorder::Initialize();
-}
-
-UMAHistogramHelper::~UMAHistogramHelper() {
-}
-
-void UMAHistogramHelper::PrepareSnapshot(const char* const histogram_names[],
-                                         size_t num_histograms) {
-  for (size_t i = 0; i < num_histograms; ++i) {
-    std::string histogram_name = histogram_names[i];
-
-    base::HistogramBase* histogram =
-        base::StatisticsRecorder::FindHistogram(histogram_name);
-    // If there is no histogram present, then don't record a snapshot. The logic
-    // in the Expect* methods will act to treat no histogram equivalent to
-    // samples with zeros.
-    if (histogram) {
-      histogram_snapshots[histogram_name] =
-          make_linked_ptr(histogram->SnapshotSamples().release());
-    }
-  }
-}
-
-void UMAHistogramHelper::Fetch() {
-  base::Closure callback = base::Bind(&UMAHistogramHelper::FetchCallback,
-                                      base::Unretained(this));
-
-  content::FetchHistogramsAsynchronously(
-      base::MessageLoop::current(),
-      callback,
-      // If this call times out, it means that a child process is not
-      // responding, which is something we should not ignore.  The timeout is
-      // set to be longer than the normal browser test timeout so that it will
-      // be prempted by the normal timeout.
-      TestTimeouts::action_max_timeout() * 2);
-  content::RunMessageLoop();
-}
-
-void UMAHistogramHelper::ExpectUniqueSample(
-    const std::string& name,
-    base::HistogramBase::Sample sample,
-    base::HistogramBase::Count expected_count) {
-  base::HistogramBase* histogram =
-      base::StatisticsRecorder::FindHistogram(name);
-  EXPECT_NE(static_cast<base::HistogramBase*>(NULL), histogram)
-      << "Histogram \"" << name << "\" does not exist.";
-
-  if (histogram) {
-    scoped_ptr<base::HistogramSamples> samples(histogram->SnapshotSamples());
-    CheckBucketCount(name, sample, expected_count, *samples);
-    CheckTotalCount(name, expected_count, *samples);
-  }
-}
-
-void UMAHistogramHelper::ExpectBucketCount(
-    const std::string& name,
-    base::HistogramBase::Sample sample,
-    base::HistogramBase::Count expected_count) {
-  base::HistogramBase* histogram =
-      base::StatisticsRecorder::FindHistogram(name);
-  EXPECT_NE(static_cast<base::HistogramBase*>(NULL), histogram)
-      << "Histogram \"" << name << "\" does not exist.";
-
-  if (histogram) {
-    scoped_ptr<base::HistogramSamples> samples(histogram->SnapshotSamples());
-    CheckBucketCount(name, sample, expected_count, *samples);
-  }
-}
-
-void UMAHistogramHelper::ExpectTotalCount(
-    const std::string& name,
-    base::HistogramBase::Count count) {
-  base::HistogramBase* histogram =
-      base::StatisticsRecorder::FindHistogram(name);
-  if (histogram) {
-    scoped_ptr<base::HistogramSamples> samples(histogram->SnapshotSamples());
-    CheckTotalCount(name, count, *samples);
-  } else {
-    // No histogram means there were zero samples.
-    EXPECT_EQ(count, 0) << "Histogram \"" << name << "\" does not exist.";
-  }
-}
-
-void UMAHistogramHelper::FetchCallback() {
-  base::MessageLoopForUI::current()->Quit();
-}
-
-void UMAHistogramHelper::CheckBucketCount(
-    const std::string& name,
-    base::HistogramBase::Sample sample,
-    base::HistogramBase::Count expected_count,
-    base::HistogramSamples& samples) {
-  int actual_count = samples.GetCount(sample);
-  if (histogram_snapshots.count(name))
-    actual_count -= histogram_snapshots[name]->GetCount(sample);
-  EXPECT_EQ(expected_count, actual_count)
-      << "Histogram \"" << name
-      << "\" does not have the right number of samples (" << expected_count
-      << ") in the expected bucket (" << sample << "). It has (" << actual_count
-      << ").";
-}
-
-void UMAHistogramHelper::CheckTotalCount(
-    const std::string& name,
-    base::HistogramBase::Count expected_count,
-    base::HistogramSamples& samples) {
-  int actual_count = samples.TotalCount();
-  if (histogram_snapshots.count(name))
-    actual_count -= histogram_snapshots[name]->TotalCount();
-  EXPECT_EQ(expected_count, actual_count)
-      << "Histogram \"" << name
-      << "\" does not have the right total number of samples ("
-      << expected_count << "). It has (" << actual_count << ").";
-}