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

components/password_manager/core/browser/password_store_default.h

Index: components/password_manager/core/browser/password_store_default.h
diff --git a/components/password_manager/core/browser/password_store_default.h b/components/password_manager/core/browser/password_store_default.h
index 7f42c192fd373401de4f33704211c8a71f0e4305..02a496cab030d1fbce743e6c73d1cedee689a5fa 100644
--- a/components/password_manager/core/browser/password_store_default.h
+++ b/components/password_manager/core/browser/password_store_default.h
@@ -21,11 +21,21 @@ class PasswordStoreDefault : public PasswordStore {
   PasswordStoreDefault(
       scoped_refptr<base::SingleThreadTaskRunner> main_thread_runner,
       scoped_refptr<base::SingleThreadTaskRunner> db_thread_runner,
-      LoginDatabase* login_db);
+      const base::FilePath& login_db_file_path);
+
+  bool Init(const syncer::SyncableService::StartSyncFlare& flare) override;
+
+  // Used 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;
@@ -57,6 +67,10 @@ class PasswordStoreDefault : public PasswordStore {
   }
 
  private:
+  base::FilePath login_db_file_path_;
+
+  // The SQLite login database, opened on the DB thread in a deferred manner.
+  // Will be NULL for the lifetime of |this| if opening fails.
   scoped_ptr<LoginDatabase> login_db_;
 
   DISALLOW_COPY_AND_ASSIGN(PasswordStoreDefault);