Reporting: Add histograms.

net/reporting/reporting_network_change_observer.cc

Index: net/reporting/reporting_network_change_observer.cc
diff --git a/net/reporting/reporting_network_change_observer.cc b/net/reporting/reporting_network_change_observer.cc
index 6c62b7f57a49aaf457fd70848d6eec5d58d1b6b8..99bb5a66f8a81152c755cc74ec1bf7500131f212 100644
--- a/net/reporting/reporting_network_change_observer.cc
+++ b/net/reporting/reporting_network_change_observer.cc
@@ -9,6 +9,7 @@
 #include "net/reporting/reporting_cache.h"
 #include "net/reporting/reporting_context.h"
 #include "net/reporting/reporting_policy.h"
+#include "net/reporting/reporting_report.h"
 
 namespace net {
 
@@ -38,7 +39,8 @@ class ReportingNetworkChangeObserverImpl
       return;
 
     if (context_->policy().clear_reports_on_network_changes)
-      context_->cache()->RemoveAllReports();
+      context_->cache()->RemoveAllReports(
+          ReportingReport::Outcome::ERASED_NETWORK_CHANGED);
 
     if (context_->policy().clear_clients_on_network_changes)
       context_->cache()->RemoveAllClients();