Create and pass shared-histogram-allocator from browser to renderer.

base/metrics/persistent_histogram_allocator.h

Index: base/metrics/persistent_histogram_allocator.h
diff --git a/base/metrics/persistent_histogram_allocator.h b/base/metrics/persistent_histogram_allocator.h
index 12ac68500cb202c63ff8e813d6b16762022f6e85..b2038c4314c704f572771648b76410fdcffd03b0 100644
--- a/base/metrics/persistent_histogram_allocator.h
+++ b/base/metrics/persistent_histogram_allocator.h
@@ -116,13 +116,6 @@ class BASE_EXPORT PersistentHistogramAllocator {
   // Histogram containing creation results. Visible for testing.
   static HistogramBase* GetCreateHistogramResultHistogram();
 
-  // This access to the persistent allocator is only for testing; it extracts
-  // the current allocator completely. This allows easy creation of histograms
-  // within persistent memory segments which can then be extracted and used
-  // in other ways.
-  static std::unique_ptr<PersistentHistogramAllocator>
-  ReleaseGlobalAllocatorForTesting();
-
  protected:
   // The structure used to hold histogram data in persistent memory. It is
   // defined and used entirely within the .cc file.