Break global impact of PersistentHistogramAllocator into a separate class.

base/metrics/sparse_histogram.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 "base/metrics/sparse_histogram.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "base/metrics/metrics_hashes.h"
 #include "base/metrics/persistent_histogram_allocator.h"
 #include "base/metrics/persistent_sample_map.h"
 #include "base/metrics/sample_map.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/pickle.h"
 #include "base/strings/stringprintf.h"
 #include "base/synchronization/lock.h"
 
 namespace base {
 
 typedef HistogramBase::Count Count;
 typedef HistogramBase::Sample Sample;
 
 // static
 HistogramBase* SparseHistogram::FactoryGet(const std::string& name,
                                            int32_t flags) {
-  // Import histograms from known persistent storage. Histograms could have
-  // been added by other processes and they must be fetched and recognized
-  // locally in order to be found by FindHistograms() below. If the persistent
-  // memory segment is not shared between processes, this call does nothing.
-  PersistentHistogramAllocator::ImportGlobalHistograms();
-
   HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
   if (!histogram) {
     // Try to create the histogram using a "persistent" allocator. As of
     // 2016-02-25, the availability of such is controlled by a base::Feature
     // that is off by default. If the allocator doesn't exist or if
     // allocating from it fails, code below will allocate the histogram from
     // the process heap.
     PersistentMemoryAllocator::Reference histogram_ref = 0;
     std::unique_ptr<HistogramBase> tentative_histogram;
-    PersistentHistogramAllocator* allocator =
-        PersistentHistogramAllocator::GetGlobalAllocator();
+    PersistentHistogramAllocator* allocator = GlobalHistogramAllocator::Get();
     if (allocator) {
       tentative_histogram = allocator->AllocateHistogram(
           SPARSE_HISTOGRAM, name, 0, 0, nullptr, flags, &histogram_ref);
     }
 
     // Handle the case where no persistent allocator is present or the
     // persistent allocation fails (perhaps because it is full).
     if (!tentative_histogram) {
       DCHECK(!histogram_ref);  // Should never have been set.
       DCHECK(!allocator);      // Shouldn't have failed.
@@ skipping 219 matching lines @@
                                        std::string* output) const {
   StringAppendF(output,
                 "Histogram: %s recorded %d samples",
                 histogram_name().c_str(),
                 total_count);
   if (flags() & ~kHexRangePrintingFlag)
     StringAppendF(output, " (flags = 0x%x)", flags() & ~kHexRangePrintingFlag);
 }
 
 }  // namespace base