[SyncFS] Run ConflictResolver only when it is needed.

chrome/browser/sync_file_system/drive_backend/sync_engine.h

Index: chrome/browser/sync_file_system/drive_backend/sync_engine.h
diff --git a/chrome/browser/sync_file_system/drive_backend/sync_engine.h b/chrome/browser/sync_file_system/drive_backend/sync_engine.h
index a64da99c6ea6357aca31a4d3f2f21f6fea3f4f55..8172b4f60ecff5c494eee3c2c057785b1f1ddb59 100644
--- a/chrome/browser/sync_file_system/drive_backend/sync_engine.h
+++ b/chrome/browser/sync_file_system/drive_backend/sync_engine.h
@@ -145,9 +145,11 @@ class SyncEngine : public RemoteFileSyncService,
   void DidApplyLocalChange(LocalToRemoteSyncer* syncer,
                            const SyncStatusCallback& callback,
                            SyncStatusCode status);
-  void DidFetchChangeList(SyncStatusCallback& callback);
 
   void MaybeStartFetchChanges();
+  void DidResolveConflict(SyncStatusCode status);
+  void DidFetchChanges(SyncStatusCode status);
+
   void UpdateServiceStateFromSyncStatusCode(SyncStatusCode state,
                                             bool used_network);
   void UpdateServiceState(RemoteServiceState state,
@@ -176,6 +178,7 @@ class SyncEngine : public RemoteFileSyncService,
 
   RemoteServiceState service_state_;
 
+  bool should_check_conflict_;
   bool should_check_remote_change_;
   base::TimeTicks time_to_check_changes_;