Merge subprocess metrics into global StatisticsRecorder.

components/metrics/metrics_service.cc

Index: components/metrics/metrics_service.cc
diff --git a/components/metrics/metrics_service.cc b/components/metrics/metrics_service.cc
index 120fc6daa97101d8d957937345f5b8906b9e3210..eb6996bf8e3c81cbcfe744146236761d1a843d8e 100644
--- a/components/metrics/metrics_service.cc
+++ b/components/metrics/metrics_service.cc
@@ -1119,6 +1119,11 @@ void MetricsService::RecordCurrentEnvironment(MetricsLog* log) {
 
 void MetricsService::RecordCurrentHistograms() {
   DCHECK(log_manager_.current_log());
+
+  // Merge any data from metrics providers into the global StatisticsRecorder.
+  for (MetricsProvider* provider : metrics_providers_)
+    provider->MergeHistogramDeltas();
+
   histogram_snapshot_manager_.StartDeltas();
   // "true" to the begin() call indicates that StatisticsRecorder should include
   // histograms held in persistent storage.