[Sync] Try to fix race conditions in CookieJarMismatch.

components/sync/driver/glue/sync_backend_host_impl.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/sync/driver/glue/sync_backend_host_impl.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 413 matching lines @@
 
 void SyncBackendHostImpl::ClearServerData(
     const SyncManager::ClearServerDataCallback& callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
   sync_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&SyncBackendHostCore::DoClearServerData, core_, callback));
 }
 
 void SyncBackendHostImpl::OnCookieJarChanged(bool account_mismatch,
-                                             bool empty_jar) {
+                                             bool empty_jar,
+                                             const base::Closure& callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
   sync_task_runner_->PostTask(
       FROM_HERE, base::Bind(&SyncBackendHostCore::DoOnCookieJarChanged, core_,
-                            account_mismatch, empty_jar));
+                            account_mismatch, empty_jar, callback));
 }
 
 void SyncBackendHostImpl::ClearServerDataDoneOnFrontendLoop(
     const SyncManager::ClearServerDataCallback& frontend_callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
   frontend_callback.Run();
 }
 
+void SyncBackendHostImpl::OnCookieJarChangedDoneOnFrontendLoop(
+    const base::Closure& callback) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  callback.Run();
+}
+
 }  // namespace syncer
 
 #undef SDVLOG
 
 #undef SLOG