Added HistoryService::GetHistoryCount() and helper functions in components/history

components/history/core/browser/history_service.h

Index: components/history/core/browser/history_service.h
diff --git a/components/history/core/browser/history_service.h b/components/history/core/browser/history_service.h
index f197d2bc25d83f65c7c87f2940a416c1a6930cbf..56fa1140c7252a5e9c780e0620d2bff7dfede1a7 100644
--- a/components/history/core/browser/history_service.h
+++ b/components/history/core/browser/history_service.h
@@ -342,6 +342,18 @@ class HistoryService : public syncer::SyncableService, public KeyedService {
       const QueryFilteredURLsCallback& callback,
       base::CancelableTaskTracker* tracker);
 
+  // Statistics ----------------------------------------------------------------
+
+  // Gets the number of URLs as seen in chrome://history with infinite date
+  // range. If a URL is visited in multiple days, the URL is counted once for
+  // each day. For determination of the date, timestamps are converted to dates
+  // using local time.
+  typedef base::Callback<void(HistoryCountResult)> GetHistoryCountCallback;
+
+  base::CancelableTaskTracker::TaskId GetHistoryCount(
+      const GetHistoryCountCallback& callback,
+      base::CancelableTaskTracker* tracker);
+
   // Database management operations --------------------------------------------
 
   // Delete all the information related to a single url.