Domain Reliability: Add more upload-related histograms.

components/domain_reliability/context.h

Index: components/domain_reliability/context.h
diff --git a/components/domain_reliability/context.h b/components/domain_reliability/context.h
index 34ef4bf9d2bdf6806773b0ee3bedc04dba7e823f..41c35a5f02a153e78277f73ad470c391b21c1fb3 100644
--- a/components/domain_reliability/context.h
+++ b/components/domain_reliability/context.h
@@ -61,7 +61,10 @@ class DOMAIN_RELIABILITY_EXPORT DomainReliabilityContext {
   // Notifies the context of a beacon on its domain(s); may or may not save the
   // actual beacon to be uploaded, depending on the sample rates in the config,
   // but will increment one of the request counters in any case.
-  void OnBeacon(std::unique_ptr<DomainReliabilityBeacon> beacon);
+  //
+  // Returns |true| if the beacon was queued or |false| if it was discarded,
+  // for metrics purposes.
+  bool OnBeacon(std::unique_ptr<DomainReliabilityBeacon> beacon);
 
   // Called to clear browsing data, since beacons are like browsing history.
   void ClearBeacons();
@@ -122,6 +125,8 @@ class DOMAIN_RELIABILITY_EXPORT DomainReliabilityContext {
   // pointer to that value in a wider (e.g. per-Monitor or unittest) scope.
   const base::TimeTicks* last_network_change_time_;
 
+  base::TimeTicks last_queued_beacon_time_;
+
   base::WeakPtrFactory<DomainReliabilityContext> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DomainReliabilityContext);