[Sync] Try to fix race conditions in CookieJarMismatch.

components/sync/engine/sync_engine.h

Index: components/sync/engine/sync_engine.h
diff --git a/components/sync/engine/sync_engine.h b/components/sync/engine/sync_engine.h
index 581c74a00333948f540d96b5d79771da6cf6270f..09c32e8c404cbcff65c3be1e94013f93fdf1a37e 100644
--- a/components/sync/engine/sync_engine.h
+++ b/components/sync/engine/sync_engine.h
@@ -186,7 +186,9 @@ class SyncEngine : public ModelTypeConfigurer {
 
   // Notify the syncer that the cookie jar has changed.
   // See SyncManager::OnCookieJarChanged.
-  virtual void OnCookieJarChanged(bool account_mismatch, bool empty_jar) = 0;
+  virtual void OnCookieJarChanged(bool account_mismatch,
+                                  bool empty_jar,
+                                  const base::Closure& callback) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SyncEngine);