[Sync] ModelTypeStore factory shouldn't require valid PSS to function correctly

components/sync/driver/fake_sync_client.h

 // Copyright 2015 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.
 
 #ifndef COMPONENTS_SYNC_DRIVER_FAKE_SYNC_CLIENT_H_
 #define COMPONENTS_SYNC_DRIVER_FAKE_SYNC_CLIENT_H_
 
 #include <memory>
 
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "components/sync/driver/sync_client.h"
 #include "components/sync_preferences/testing_pref_service_syncable.h"
 
 namespace syncer {
 
 class FakeSyncService;
 
 // Fake implementation of SyncClient interface for tests.
 class FakeSyncClient : public SyncClient {
  public:
   FakeSyncClient();
   explicit FakeSyncClient(SyncApiComponentFactory* factory);
   ~FakeSyncClient() override;
 
   void Initialize() override;
 
+  base::SequencedWorkerPool* GetBlockingPool() override;
   SyncService* GetSyncService() override;
   PrefService* GetPrefService() override;
   base::FilePath GetLocalSyncBackendFolder() override;
   bookmarks::BookmarkModel* GetBookmarkModel() override;
   favicon::FaviconService* GetFaviconService() override;
   history::HistoryService* GetHistoryService() override;
   bool HasPasswordStore() override;
   base::Closure GetPasswordStateChangedCallback() override;
   SyncApiComponentFactory::RegisterDataTypesMethod
   GetRegisterPlatformTypesCallback() override;
@@ skipping 17 matching lines @@
   ModelTypeSyncBridge* bridge_;
   SyncApiComponentFactory* factory_;
   std::unique_ptr<FakeSyncService> sync_service_;
 
   DISALLOW_COPY_AND_ASSIGN(FakeSyncClient);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_DRIVER_FAKE_SYNC_CLIENT_H_