Rework UMAHistogramHelper and StatisticsDeltaReader into [Chrome]HistogramTester.

base/test/statistics_delta_reader.h

-// 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.
-
-#ifndef BASE_TEST_STATISTICS_DELTA_READER_H_
-#define BASE_TEST_STATISTICS_DELTA_READER_H_
-
-#include <map>
-#include <string>
-
-#include "base/basictypes.h"
-#include "base/memory/scoped_ptr.h"
-
-namespace base {
-
-class HistogramSamples;
-
-// This class acts as a differential reader for histogram samples, enabling
-// tests to check that metrics were recorded as they should be.
-//
-// This class is DEPRECATED.
-// TODO(mlerman): Remove all references to this class with UMAHistogramHelper
-// references. crbug.com/384011
-class StatisticsDeltaReader {
- public:
-  StatisticsDeltaReader();
-  ~StatisticsDeltaReader();
-
-  // Returns the histogram data accumulated since this instance was created.
-  // Returns NULL if no samples are available.
-  scoped_ptr<HistogramSamples> GetHistogramSamplesSinceCreation(
-      const std::string& histogram_name);
-
- private:
-  // Used to determine the histogram changes made during this instance's
-  // lifecycle. This instance takes ownership of the samples, which are deleted
-  // when the instance is destroyed.
-  std::map<std::string, HistogramSamples*> original_samples_;
-
-  DISALLOW_COPY_AND_ASSIGN(StatisticsDeltaReader);
-};
-
-}  // namespace base
-
-#endif  // BASE_TEST_STATISTICS_DELTA_READER_H_