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

components/safe_browsing_db/v4_get_hash_protocol_manager.h

Index: components/safe_browsing_db/v4_get_hash_protocol_manager.h
diff --git a/components/safe_browsing_db/v4_get_hash_protocol_manager.h b/components/safe_browsing_db/v4_get_hash_protocol_manager.h
index 720e09684cb42c8aa55c2007a5e243e5ec893624..fb736d905da5fe047256ef3855c4958c3401f923 100644
--- a/components/safe_browsing_db/v4_get_hash_protocol_manager.h
+++ b/components/safe_browsing_db/v4_get_hash_protocol_manager.h
@@ -106,7 +106,8 @@ struct FullHashCallbackInfo {
                        std::unique_ptr<net::URLFetcher> fetcher,
                        const FullHashToStoreAndHashPrefixesMap&
                            full_hash_to_store_and_hash_prefixes,
-                       const FullHashCallback& callback);
+                       const FullHashCallback& callback,
+                       const base::Time& network_start_time);
   ~FullHashCallbackInfo();
 
   // The FullHashInfo objects retrieved from cache. These are merged with the
@@ -125,6 +126,10 @@ struct FullHashCallbackInfo {
   // which to look for a full hash match.
   FullHashToStoreAndHashPrefixesMap full_hash_to_store_and_hash_prefixes;
 
+  // Used to measure how long did it take to fetch the full hash response from
+  // the server.
+  base::Time network_start_time;
+
   // The prefixes that were requested from the server.
   std::vector<HashPrefix> prefixes_requested;
 };