Set site engagement timestamps to privacy-respectful values when history is cleared.

components/history/core/browser/history_backend.h

Index: components/history/core/browser/history_backend.h
diff --git a/components/history/core/browser/history_backend.h b/components/history/core/browser/history_backend.h
index 573a4010188716cfd4d0fb9c099330fae488fafd..dc971434b0de92af79b062b84a57774fdd40c0d2 100644
--- a/components/history/core/browser/history_backend.h
+++ b/components/history/core/browser/history_backend.h
@@ -213,11 +213,12 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
   // generating internal metrics.
   TopHostsList TopHosts(size_t num_hosts) const;
 
-  // Gets the counts of URLs that belong to |origins| in the history database.
-  // Origins that are not in the history database will be in the map with a
-  // count of 0.
+  // Gets the counts and last last time of URLs that belong to |origins| in the
+  // history database. Origins that are not in the history database will be in
+  // the map with a count and time of 0.
   // Returns an empty map if db_ is not initialized.
-  OriginCountMap GetCountsForOrigins(const std::set<GURL>& origins) const;
+  OriginCountAndLastVisitMap GetCountsAndLastVisitForOrigins(
+      const std::set<GURL>& origins) const;
 
   // Returns, for the given URL, a 0-based index into the list produced by
   // TopHosts(), corresponding to that URL's host. If TopHosts() has not
@@ -557,7 +558,7 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, TopHosts_IgnoreUnusualURLs);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, HostRankIfAvailable);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, RecordTopHostsMetrics);
-  FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, GetCountsForOrigins);
+  FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, GetCountsAndLastVisitForOrigins);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, UpdateVisitDuration);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, ExpireHistoryForTimes);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, DeleteFTSIndexDatabases);