PVer4: Add UMA metrics for time taken to: load DB, do prefix check,

components/safe_browsing_db/v4_local_database_manager.h

Index: components/safe_browsing_db/v4_local_database_manager.h
diff --git a/components/safe_browsing_db/v4_local_database_manager.h b/components/safe_browsing_db/v4_local_database_manager.h
index a5bdef46ae48c68c2802c375f7d8703c4910e09b..f4996474ba227c32959506c422b1162374792ab3 100644
--- a/components/safe_browsing_db/v4_local_database_manager.h
+++ b/components/safe_browsing_db/v4_local_database_manager.h
@@ -109,6 +109,11 @@ class V4LocalDatabaseManager : public SafeBrowsingDatabaseManager {
     // The threat verdict for the URL being checked.
     SBThreatType result_threat_type;
 
+    // When the check was sent to the SafeBrowsing service. Used to record the
+    // time it takes to get the uncached full hashes from the service (or a
+    // cached full hash response).
+    base::TimeTicks full_hash_check_start;
+
     // The SafeBrowsing lists to check hash prefixes in.
     StoresToCheck stores_to_check;