Introduce the PlatformNotificationContext class.

content/browser/notifications/notification_database.cc

 // 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.
 
 #include "content/browser/notifications/notification_database.h"
 
 #include <string>
 
 #include "base/files/file_util.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 53 matching lines @@
                             kKeySeparator,
                             base::Int64ToString(notification_id).c_str());
 }
 
 }  // namespace
 
 NotificationDatabase::NotificationDatabase(const base::FilePath& path)
     : path_(path),
       next_notification_id_(0),
       state_(STATE_UNINITIALIZED) {
-  sequence_checker_.DetachFromSequence();
 }
 
 NotificationDatabase::~NotificationDatabase() {
   DCHECK(sequence_checker_.CalledOnValidSequencedThread());
 }
 
 NotificationDatabase::Status NotificationDatabase::Open(
     bool create_if_missing) {
   DCHECK(sequence_checker_.CalledOnValidSequencedThread());
   DCHECK_EQ(STATE_UNINITIALIZED, state_);
@@ skipping 145 matching lines @@
   if (!base::StringToInt64(value, &next_notification_id) ||
       next_notification_id < kFirstNotificationId) {
     return STATUS_ERROR_CORRUPTED;
   }
 
  *notification_id = next_notification_id;
   return STATUS_OK;
 }
 
 }  // namespace content