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

content/browser/notifications/platform_notification_context_impl.cc

Index: content/browser/notifications/platform_notification_context_impl.cc
diff --git a/content/browser/notifications/platform_notification_context_impl.cc b/content/browser/notifications/platform_notification_context_impl.cc
index 9028997002c64d7f9404f52c5a78205f375d7493..8ee48789abec0d3f0bf85566ce38077e7da4ef08 100644
--- a/content/browser/notifications/platform_notification_context_impl.cc
+++ b/content/browser/notifications/platform_notification_context_impl.cc
@@ -69,7 +69,7 @@ void PlatformNotificationContextImpl::Initialize() {
     // 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;
     }
   }