[Sync] Try to fix race conditions in CookieJarMismatch.

components/sync/driver/glue/sync_backend_host_core.cc

Index: components/sync/driver/glue/sync_backend_host_core.cc
diff --git a/components/sync/driver/glue/sync_backend_host_core.cc b/components/sync/driver/glue/sync_backend_host_core.cc
index e2f19544a4b56aedb367996c1e4c06022e460c82..4c869565117d2238f9ea7eb8a9327ee5e7548a36 100644
--- a/components/sync/driver/glue/sync_backend_host_core.cc
+++ b/components/sync/driver/glue/sync_backend_host_core.cc
@@ -585,9 +585,15 @@ void SyncBackendHostCore::DoClearServerData(
 }
 
 void SyncBackendHostCore::DoOnCookieJarChanged(bool account_mismatch,
-                                               bool empty_jar) {
+                                               bool empty_jar,
+                                               const base::Closure& callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
   sync_manager_->OnCookieJarChanged(account_mismatch, empty_jar);
+  if (!callback.is_null()) {
+    host_.Call(FROM_HERE,
+               &SyncBackendHostImpl::OnCookieJarChangedDoneOnFrontendLoop,
+               callback);
+  }
 }
 
 void SyncBackendHostCore::ClearServerDataDone(