Move browsing_data counter sync tests to separate file

components/browsing_data/core/counters/history_counter.cc

Index: components/browsing_data/core/counters/history_counter.cc
diff --git a/components/browsing_data/core/counters/history_counter.cc b/components/browsing_data/core/counters/history_counter.cc
index 6fcb1c17ea94ec4a88a6225c190ccf4e7fd2ce78..ee93c1265d516e13bb4c1955e6cbd3914c3e0744 100644
--- a/components/browsing_data/core/counters/history_counter.cc
+++ b/components/browsing_data/core/counters/history_counter.cc
@@ -150,16 +150,9 @@ void HistoryCounter::MergeResults() {
     return;
 
   ReportResult(
-      base::MakeUnique<HistoryResult>(this, local_result_, has_synced_visits_));
+      base::MakeUnique<SyncResult>(this, local_result_, has_synced_visits_));
 }
 
-HistoryCounter::HistoryResult::HistoryResult(const HistoryCounter* source,
-                                             ResultInt value,
-                                             bool has_synced_visits)
-    : FinishedResult(source, value), has_synced_visits_(has_synced_visits) {}
-
-HistoryCounter::HistoryResult::~HistoryResult() {}
-
 void HistoryCounter::OnStateChanged(syncer::SyncService* sync) {
   bool history_sync_enabled_new_state = !!web_history_service_callback_.Run();