Merge subprocess metrics into global StatisticsRecorder.

base/metrics/statistics_recorder.h

Index: base/metrics/statistics_recorder.h
diff --git a/base/metrics/statistics_recorder.h b/base/metrics/statistics_recorder.h
index 6c436c292e6987027276e0cdee49e60787ba1280..cab832fa3baf1f54d5e9431e0b86c9eb8e5ac3b5 100644
--- a/base/metrics/statistics_recorder.h
+++ b/base/metrics/statistics_recorder.h
@@ -26,6 +26,8 @@
 #include "base/metrics/histogram_base.h"
 #include "base/strings/string_piece.h"
 
+class SubprocessMetricsProviderTest;
+
 namespace base {
 
 class BucketRanges;
@@ -185,6 +187,7 @@ class BASE_EXPORT StatisticsRecorder {
   typedef std::map<uint32_t, std::list<const BucketRanges*>*> RangesMap;
 
   friend struct DefaultLazyInstanceTraits<StatisticsRecorder>;
+  friend class ::SubprocessMetricsProviderTest;
   friend class HistogramBaseTest;
   friend class HistogramSnapshotManagerTest;
   friend class HistogramTest;