Move browsing_data counter sync tests to separate file

components/browsing_data/core/counters/history_counter.h

Index: components/browsing_data/core/counters/history_counter.h
diff --git a/components/browsing_data/core/counters/history_counter.h b/components/browsing_data/core/counters/history_counter.h
index f06ca6154afec8a7bd1ece7cfdf49b95f982450c..9457b8912fc81ca43ca26025ab44e3d4a89d15df 100644
--- a/components/browsing_data/core/counters/history_counter.h
+++ b/components/browsing_data/core/counters/history_counter.h
@@ -23,19 +23,6 @@ class HistoryCounter : public browsing_data::BrowsingDataCounter,
   typedef base::Callback<history::WebHistoryService*()>
       GetUpdatedWebHistoryServiceCallback;
 
-  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_;
-  };
-
   explicit HistoryCounter(history::HistoryService* history_service,
                           const GetUpdatedWebHistoryServiceCallback& callback,
                           syncer::SyncService* sync_service);