Replace c/b/nss_context by a KeyedService.

components/cert_database/public/cert_database_service_io_part.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_CERT_DATABASE_PUBLIC_CERT_DATABASE_SERVICE_IO_PART_H_
+#define COMPONENTS_CERT_DATABASE_PUBLIC_CERT_DATABASE_SERVICE_IO_PART_H_
+
+#include <vector>
+
+#include "base/callback_forward.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/threading/thread_checker.h"
+
+namespace net {
+class NSSCertDatabase;
+}
+
+namespace cert_database {
+
+// Any object of this class is constructed on the UI thread. Afterward it is
+// initialized on the IO thread, it may only be accessed on IO thread.
+class CertDatabaseServiceIOPart {
+ public:
+  typedef base::Callback<void(net::NSSCertDatabase*)> GetCertDBCallback;
+
+  CertDatabaseServiceIOPart();
+  virtual ~CertDatabaseServiceIOPart();
+
+  virtual void Init();
+
+  // Returns the NSSCertDatabase synchronously if it is already available.
+  // Otherwise passes it asynchronously to |callback| once it is available.
+  WARN_UNUSED_RESULT net::NSSCertDatabase* GetNSSCertDatabase(
+      const GetCertDBCallback& callback);
+
+  base::WeakPtr<CertDatabaseServiceIOPart> GetWeakPtr();
+
+ protected:
+  // Returns false until Init() is called.
+  bool IsInitialized();
+
+  // Stores |db| and calls all pending GetNSSCertDatabase callbacks.
+  void SetNSSCertDatabase(scoped_ptr<net::NSSCertDatabase> db);
+
+  base::ThreadChecker thread_checker_;

[Joao da Silva, 2014/10/30 09:48:01]

Inherit from NonThreadSafe instead

[pneubeck (no reviews), 2014/11/05 14:53:37]

made the member private, in which case the member is the preferred way,
according to ThreadChecker's documentation.

+
+ private:
+  // False until Init() is called.
+  bool initialized_;
+
+  scoped_ptr<net::NSSCertDatabase> nss_cert_database_;
+  std::vector<GetCertDBCallback> get_cert_db_callbacks_;
+  base::WeakPtrFactory<CertDatabaseServiceIOPart> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(CertDatabaseServiceIOPart);
+};
+
+}  // namespace cert_database
+
+#endif  // COMPONENTS_CERT_DATABASE_PUBLIC_CERT_DATABASE_SERVICE_IO_PART_H_