Break global impact of PersistentHistogramAllocator into a separate class.

base/metrics/histogram_unittest.cc

Index: base/metrics/histogram_unittest.cc
diff --git a/base/metrics/histogram_unittest.cc b/base/metrics/histogram_unittest.cc
index 4fa0aa58ec08d35e0fa923a9d58700d5a575906e..a908d786119f1806222be9f35fbebb1de1eff558 100644
--- a/base/metrics/histogram_unittest.cc
+++ b/base/metrics/histogram_unittest.cc
@@ -68,17 +68,16 @@ class HistogramTest : public testing::TestWithParam<bool> {
     // By getting the results-histogram before any persistent allocator
     // is attached, that histogram is guaranteed not to be stored in
     // any persistent memory segment (which simplifies some tests).
-    PersistentHistogramAllocator::GetCreateHistogramResultHistogram();
+    GlobalHistogramAllocator::GetCreateHistogramResultHistogram();
 
-    PersistentHistogramAllocator::CreateGlobalAllocatorOnLocalMemory(
+    GlobalHistogramAllocator::CreateWithLocalMemory(
         kAllocatorMemorySize, 0, "HistogramAllocatorTest");
-    allocator_ =
-        PersistentHistogramAllocator::GetGlobalAllocator()->memory_allocator();
+    allocator_ = GlobalHistogramAllocator::Get()->memory_allocator();
   }
 
   void DestroyPersistentHistogramAllocator() {
     allocator_ = nullptr;
-    PersistentHistogramAllocator::ReleaseGlobalAllocatorForTesting();
+    GlobalHistogramAllocator::ReleaseForTesting();
   }
 
   const bool use_persistent_histogram_allocator_;