Polish the result communication and display of the browsing data counters.

chrome/browser/browsing_data/history_counter.h

 // Copyright (c) 2015 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 CHROME_BROWSER_BROWSING_DATA_HISTORY_COUNTER_H_
 #define CHROME_BROWSER_BROWSING_DATA_HISTORY_COUNTER_H_
 
 #include "base/task/cancelable_task_tracker.h"
 #include "base/timer/timer.h"
 #include "chrome/browser/browsing_data/browsing_data_counter.h"
 #include "components/history/core/browser/history_service.h"
 #include "components/history/core/browser/web_history_service.h"
 
 class HistoryCounter: public BrowsingDataCounter {
  public:
-  // A special value indicating that the local counting result is zero, but some
-  // history entries exist in Sync.
-  // TODO(msramek): Change the callback signature so we can return a structured
-  // result instead of special int values.
-  static const BrowsingDataCounter::ResultInt kOnlySyncedHistory;
+  class HistoryResult : public FinishedResult {
+   public:
+    HistoryResult(const HistoryCounter* source,
+                  ResultInt value,
+                  bool has_synced_visits);
+    ~HistoryResult() override;
+
+    bool has_synced_visits() const { return has_synced_visits_; }
+
+   private:
+    bool has_synced_visits_;
+  };
 
   HistoryCounter();
   ~HistoryCounter() override;
 
   const std::string& GetPrefName() const override;
 
   // Whether there are counting tasks in progress. Only used for testing.
   bool HasTrackedTasks();
 
   // Make the history counter use a custom WebHistoryService instance. Only
@@ skipping 20 matching lines @@
   void Count() override;
 
   void OnGetLocalHistoryCount(history::HistoryCountResult result);
   void OnGetWebHistoryCount(history::WebHistoryService::Request* request,
                             const base::DictionaryValue* result);
   void OnWebHistoryTimeout();
   void MergeResults();
 };
 
 #endif  // CHROME_BROWSER_BROWSING_DATA_HISTORY_COUNTER_H_