Break global impact of PersistentHistogramAllocator into a separate class.

base/metrics/histogram.cc

Index: base/metrics/histogram.cc
diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index 35197e26e395a9d08bd4bd9826938241e37754fe..2785e1b3ed2a883d1101690ebdc48b08941cf0f7 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -146,12 +146,6 @@ class Histogram::Factory {
 };
 
 HistogramBase* Histogram::Factory::Build() {
-  // 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) {
     // To avoid racy destruction at shutdown, the following will be leaked.
@@ -177,8 +171,7 @@ HistogramBase* Histogram::Factory::Build() {
     // the process heap.
     PersistentHistogramAllocator::Reference histogram_ref = 0;
     scoped_ptr<HistogramBase> tentative_histogram;
-    PersistentHistogramAllocator* allocator =
-        PersistentHistogramAllocator::GetGlobalAllocator();
+    PersistentHistogramAllocator* allocator = GlobalHistogramAllocator::Get();
     if (allocator) {
       tentative_histogram = allocator->AllocateHistogram(
           histogram_type_,