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

components/history/core/browser/history_service.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_HISTORY_CORE_BROWSER_HISTORY_SERVICE_H_
 #define COMPONENTS_HISTORY_CORE_BROWSER_HISTORY_SERVICE_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 324 matching lines @@
   typedef base::Callback<void(const FilteredURLList*)>
       QueryFilteredURLsCallback;
 
   base::CancelableTaskTracker::TaskId QueryFilteredURLs(
       int result_count,
       const VisitFilter& filter,
       bool extended_info,
       const QueryFilteredURLsCallback& callback,
       base::CancelableTaskTracker* tracker);
 
+  // Statistics ----------------------------------------------------------------
+
+  // Returns the count of URLs in the url database. The argument is the count.

[msramek, 2015/09/14 17:28:16]

I'd suggest omitting this comment. The fact that this is used in
|GetHistoryCount| gives a clear picture what this callback is for.

Furthermore, count = 0 does not indicate database failure, but success = false
does. You could add that to the |GetHistoryCount| comment.

[lwchkg, 2015/09/15 14:27:08]

Thanks. Just forgot to update the comment here.

+  // The count is zero if query to the database failed.
+  typedef base::Callback<void(HistoryCountResult)> GetHistoryCountCallback;

[msramek, 2015/09/14 17:28:16]

This shouldn't be called "Get", as it's not a getter.

[lwchkg, 2015/09/15 14:27:08]

Puzzled here. This is the callback function in GetHistoryCount, so it's called
GetHistoryCountCallback according the the naming conventions in this file.

[msramek, 2015/09/16 11:16:30]

Oh... of course :) Sorry for that.

+
+  // Returns the count of URLs in the url database.

[msramek, 2015/09/14 17:28:16]

Please update the comment to explain that we're counting distinct URLs per day.

[lwchkg, 2015/09/15 14:27:08]

Acknowledged.

+  base::CancelableTaskTracker::TaskId GetHistoryCount(
+      const GetHistoryCountCallback& callback,
+      base::CancelableTaskTracker* tracker);
+
   // Database management operations --------------------------------------------
 
   // Delete all the information related to a single url.
   void DeleteURL(const GURL& url);
 
   // Delete all the information related to a list of urls.  (Deleting
   // URLs one by one is slow as it has to flush to disk each time.)
   void DeleteURLsForTest(const std::vector<GURL>& urls);
 
   // Removes all visits in the selected time range (including the
@@ skipping 490 matching lines @@
 
   // All vended weak pointers are invalidated in Cleanup().
   base::WeakPtrFactory<HistoryService> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(HistoryService);
 };
 
 }  // namespace history
 
 #endif  // COMPONENTS_HISTORY_CORE_BROWSER_HISTORY_SERVICE_H_