Replace c/b/nss_context by a KeyedService.

components/cert_database/core/cert_database_service.cc

+// 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.
+
+#include "components/cert_database/public/cert_database_service.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/callback.h"
+#include "base/location.h"
+#include "base/single_thread_task_runner.h"
+#include "base/thread_task_runner_handle.h"
+#include "components/cert_database/public/cert_database_service_io_part.h"
+#include "net/cert/nss_cert_database.h"
+
+namespace {
+
+void CallBackOnTaskRunner(
+    const scoped_refptr<base::TaskRunner>& task_runner,
+    const CertDatabaseService::GetCertDBCallback& callback,
+    net::NSSCertDatabase* cert_db) {
+  task_runner->PostTask(FROM_HERE, base::Bind(callback, cert_db));
+}
+
+void GetNSSCertDBOnIOThread(
+    base::WeakPtr<CertDatabaseServiceIOPart> io_part,
+    const CertDatabaseService::GetCertDBCallback& callback) {
+  if (!io_part)
+    return;
+  net::NSSCertDatabase* db = io_part->GetNSSCertDatabase(callback);
+  if (db)
+    callback.Run(db);
+}
+
+void DestroyIOPart(const base::WeakPtr<CertDatabaseServiceIOPart>& io_part) {
+  if (!io_part) {
+    LOG(WARNING) << "CertDatabaseServiceIOPart already destructed.";
+    return;
+  }
+  delete io_part.get();
+}
+
+}  // namespace
+
+CertDatabaseService::CertDatabaseService(
+    const scoped_refptr<base::SequencedTaskRunner>& io_task_runner)
+    : io_task_runner_(io_task_runner), is_io_part_set_(false) {
+}
+
+CertDatabaseService::~CertDatabaseService() {
+  io_task_runner_->PostTask(FROM_HERE, base::Bind(DestroyIOPart, io_part_));
+}
+
+void CertDatabaseService::GetNSSCertDatabase(
+    const GetCertDBCallback& callback) {
+  CHECK(is_io_part_set_);
+  GetCertDBCallback callback_on_origin_thread = base::Bind(
+      &CallBackOnTaskRunner, base::ThreadTaskRunnerHandle::Get(), callback);
+  io_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&GetNSSCertDBOnIOThread, io_part_, callback_on_origin_thread));
+}
+
+void CertDatabaseService::SetIOPart(
+    scoped_ptr<CertDatabaseServiceIOPart> io_part) {
+  DCHECK(!is_io_part_set_);
+  is_io_part_set_ = true;
+  io_part_ = io_part->GetWeakPtr();
+  ignore_result(io_part.release());
+
+  // Must immediatly post to IO for initialization, so that subsequent accesses
+  // hit the IO thread after Init() was called.
+  io_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&CertDatabaseServiceIOPart::Init, io_part_));
+}
+
+base::WeakPtr<CertDatabaseServiceIOPart> CertDatabaseService::GetIOPart() {
+  CHECK(is_io_part_set_);
+  return io_part_;
+}