Rework UMAHistogramHelper and StatisticsDeltaReader into [Chrome]HistogramTester.

chrome/test/base/uma_histogram_helper.h

-// 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.
-
-#ifndef CHROME_TEST_BASE_UMA_HISTOGRAM_HELPER_H_
-#define CHROME_TEST_BASE_UMA_HISTOGRAM_HELPER_H_
-
-#include "base/memory/linked_ptr.h"
-#include "base/metrics/histogram.h"
-#include "base/metrics/histogram_base.h"
-#include "base/metrics/histogram_samples.h"
-
-// UMAHistogramHelper provides a simple interface for examining UMA histograms.
-// Tests can use this interface to verify that UMA data is getting logged as
-// intended.
-class UMAHistogramHelper {
- public:
-  // UMAHistogramHelper should be created before the execution of the test case.
-  UMAHistogramHelper();
-
-  ~UMAHistogramHelper();
-
-  // Parameters should be string literals of all histograms to snapshot.
-  // Call this before executing the test code. This method can be called
-  // multiple times. The existing snapshots are preserved, except when one of
-  // the |histogram_names| was previously passed as a parameter, then a new
-  // snapshot will replace the existing one.
-  void PrepareSnapshot(const char* const histogram_names[],
-                       size_t num_histograms);
-
-  // Each child process may have its own histogram data, make sure this data
-  // gets accumulated into the browser process before we examine the histograms.
-  void Fetch();
-
-  // We know the exact number of samples in a bucket, and that no other bucket
-  // should have samples. If |PrepareSnapshot| was called for the histogram
-  // named |name| then the |expected_count| is the diff from the snapshot.
-  void ExpectUniqueSample(const std::string& name,
-                          base::HistogramBase::Sample sample,
-                          base::HistogramBase::Count expected_count);
-
-  // We know the exact number of samples in a bucket, but other buckets may
-  // have samples as well. If |PrepareSnapshot| was called for histogram named
-  // |name| then the |expected_count| is the diff from the snapshot.
-  void ExpectBucketCount(const std::string& name,
-                          base::HistogramBase::Sample sample,
-                          base::HistogramBase::Count expected_count);
-
-  // We don't know the values of the samples, but we know how many there are. If
-  // |PrepareSnapshot| was called for |name| histogram, then the
-  // |count| is the diff from the snapshot.
-  void ExpectTotalCount(const std::string& name,
-                        base::HistogramBase::Count count);
-
- private:
-  void FetchCallback();
-
-  void CheckBucketCount(const std::string& name,
-                        base::HistogramBase::Sample sample,
-                        base::Histogram::Count expected_count,
-                        base::HistogramSamples& samples);
-
-  void CheckTotalCount(const std::string& name,
-                       base::Histogram::Count expected_count,
-                       base::HistogramSamples& samples);
-
-  DISALLOW_COPY_AND_ASSIGN(UMAHistogramHelper);
-
-  // The map from histogram names to their snapshots
-  std::map<std::string, linked_ptr<base::HistogramSamples> >
-      histogram_snapshots;
-};
-
-#endif  // CHROME_TEST_BASE_UMA_HISTOGRAM_HELPER_H_