Use container::back() and container::pop_back() for content.

content/browser/notifications/platform_notification_context_impl.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/platform_notification_context_impl.h"
 
 #include "base/bind_helpers.h"
 #include "base/files/file_util.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
@@ skipping 51 matching lines @@
     // Synchronize the notifications stored in the database with the set of
     // displaying notifications in |displayed_notifications|. This is necessary
     // because flakiness may cause a platform to inform Chrome of a notification
     // that has since been closed, or because the platform does not support
     // notifications that exceed the lifetime of the browser process.
 
     // TODO(peter): Synchronizing the actual notifications will be done when the
     // persistent notification ids are stable. For M44 we need to support the
     // case where there may be no notifications after a Chrome restart.
     if (notification_synchronization_supported &&
-        !displayed_notifications.size()) {
+        displayed_notifications.empty()) {
       prune_database_on_open_ = true;
     }
   }
 
   BrowserThread::PostTask(
       BrowserThread::IO, FROM_HERE,
       base::Bind(&PlatformNotificationContextImpl::InitializeOnIO, this));
 }
 
 void PlatformNotificationContextImpl::InitializeOnIO() {
@@ skipping 356 matching lines @@
 
   return path_.Append(kPlatformNotificationsDirectory);
 }
 
 void PlatformNotificationContextImpl::SetTaskRunnerForTesting(
     const scoped_refptr<base::SequencedTaskRunner>& task_runner) {
   task_runner_ = task_runner;
 }
 
 }  // namespace content