Check for NULL host_ or frontend_ in the sync_backend_host.

chrome/browser/sync/glue/sync_backend_host.cc

 // Copyright (c) 2010 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 "build/build_config.h"
 #include "base/file_util.h"
 #include "base/file_version_info.h"
 #include "base/task.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/app/chrome_version_info.h"
@@ skipping 520 matching lines @@
   host_->frontend_loop_->PostTask(FROM_HERE,
       NewRunnableMethod(this,
                         &Core::HandleInitalizationCompletedOnFrontendLoop));
 
   // Initialization is complete, so we can schedule recurring SaveChanges.
   host_->core_thread_.message_loop()->PostTask(FROM_HERE,
       NewRunnableMethod(this, &Core::StartSavingChanges));
 }
 
 void SyncBackendHost::Core::HandleInitalizationCompletedOnFrontendLoop() {
+  if (!host_)
+    return;
   host_->HandleInitializationCompletedOnFrontendLoop();
 }
 
 void SyncBackendHost::HandleInitializationCompletedOnFrontendLoop() {
+  if (!frontend_)
+    return;
   frontend_->OnBackendInitialized();
 }
 
 bool SyncBackendHost::Core::IsCurrentThreadSafeForModel(
     syncable::ModelType model_type) {
   AutoLock lock(host_->registrar_lock_);
 
   browser_sync::ModelSafeRoutingInfo::const_iterator routing_it =
       host_->registrar_.routing_info.find(model_type);
   if (routing_it == host_->registrar_.routing_info.end())
@@ skipping 36 matching lines @@
       FROM_HERE,
       NewRunnableMethod(this, &Core::NotifyResumed));
 }
 
 void SyncBackendHost::Core::OnStopSyncingPermanently() {
   host_->frontend_loop_->PostTask(FROM_HERE, NewRunnableMethod(this,
       &Core::HandleStopSyncingPermanentlyOnFrontendLoop));
 }
 
 void SyncBackendHost::Core::HandleStopSyncingPermanentlyOnFrontendLoop() {
+  if (!host_ || !host_->frontend_)
+    return;
   host_->frontend_->OnStopSyncingPermanently();
 }
 
 void SyncBackendHost::Core::HandleAuthErrorEventOnFrontendLoop(
     const GoogleServiceAuthError& new_auth_error) {
   if (!host_ || !host_->frontend_)
     return;
 
   DCHECK_EQ(MessageLoop::current(), host_->frontend_loop_);
 
@@ skipping 24 matching lines @@
 }
 
 void SyncBackendHost::Core::DeleteSyncDataFolder() {
   if (file_util::DirectoryExists(host_->sync_data_folder_path())) {
     if (!file_util::Delete(host_->sync_data_folder_path(), true))
       LOG(DFATAL) << "Could not delete the Sync Data folder.";
   }
 }
 
 }  // namespace browser_sync