Open the LoginDatabase on the DB thread, not the UI thread.

components/password_manager/core/browser/password_store_default.h

 // Copyright 2014 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_PASSWORD_MANAGER_CORE_BROWSER_PASSWORD_STORE_DEFAULT_H_
 #define COMPONENTS_PASSWORD_MANAGER_CORE_BROWSER_PASSWORD_STORE_DEFAULT_H_
 
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
 #include "components/password_manager/core/browser/login_database.h"
 #include "components/password_manager/core/browser/password_store.h"
 
 namespace password_manager {
 
 // Simple password store implementation that delegates everything to
 // the LoginDatabase.
 class PasswordStoreDefault : public PasswordStore {
  public:
-  // Takes ownership of |login_db|.
+  // The |login_db| must not have been Init()-ed yet. It will be initialized in
+  // a deferred manner on the DB thread.
   PasswordStoreDefault(
       scoped_refptr<base::SingleThreadTaskRunner> main_thread_runner,
       scoped_refptr<base::SingleThreadTaskRunner> db_thread_runner,
-      LoginDatabase* login_db);
+      scoped_ptr<LoginDatabase> login_db);
+
+  bool Init(const syncer::SyncableService::StartSyncFlare& flare) override;
+
+  // To be used only for testing.
+  LoginDatabase* login_db() const { return login_db_.get(); }
 
  protected:
   ~PasswordStoreDefault() override;
 
+  // Opens |login_db_| on the DB thread.
+  void InitOnDBThread();
+
   // Implements PasswordStore interface.
   void ReportMetricsImpl(const std::string& sync_username,
                          bool custom_passphrase_sync_enabled) override;
   PasswordStoreChangeList AddLoginImpl(
       const autofill::PasswordForm& form) override;
   PasswordStoreChangeList UpdateLoginImpl(
       const autofill::PasswordForm& form) override;
   PasswordStoreChangeList RemoveLoginImpl(
       const autofill::PasswordForm& form) override;
   PasswordStoreChangeList RemoveLoginsCreatedBetweenImpl(
@@ skipping 11 matching lines @@
       std::vector<autofill::PasswordForm*>* forms) override;
   bool FillBlacklistLogins(
       std::vector<autofill::PasswordForm*>* forms) override;
 
  protected:
   inline bool DeleteAndRecreateDatabaseFile() {
     return login_db_->DeleteAndRecreateDatabaseFile();
   }
 
  private:
+  // The login SQL database. The LoginDatabase instance is received via the
+  // in an uninitialized state, so as to allow injecting mocks, then Init() is
+  // called on the DB thread in a deferred manner. If opening the DB fails,
+  // |login_db_| will be reset and stay NULL for the lifetime of |this|.
   scoped_ptr<LoginDatabase> login_db_;
 
   DISALLOW_COPY_AND_ASSIGN(PasswordStoreDefault);
 };
 
 }  // namespace password_manager
 
 #endif  // COMPONENTS_PASSWORD_MANAGER_CORE_BROWSER_PASSWORD_STORE_DEFAULT_H_