* Electron Version: 3.0.0-beta.1 or 3.0.0-beta.2
* Operating System (Platform and Version): macOS 10.13 (High Sierra)
* Last known working Electron version: 2.0.4

**Expected Behavior**
When a html5 notification is triggered from the renderer, a toast alert should appear

**Actual behavior**
No toast alert is appearing when a html5 notification is triggered from the renderer

**To Reproduce**
```sh
$ git clone https://github.com/VishwasShashidhar/electron-quick-start -b notifications-3beta
$ npm install
$ npm start || electron .
```
Click on the "send notification" button in the renderer.

**Screenshots**

***Working (2.0.4)***
![electron 2 0 4 notifications](https://user-images.githubusercontent.com/5968790/42554031-ea56866e-8500-11e8-91fe-36f87b4180f9.gif)

***Not Working (3.0.0-beta.2)***
![electron 3 0 0 beta 2 notifications](https://user-images.githubusercontent.com/5968790/42554088-22da29fa-8501-11e8-8ba6-22aa765c5eac.gif)

**Additional Information**
N/A
brightray/browser/platform_notification_service.cc
#include "brightray/browser/platform_notification_service.h"
#include "base/strings/utf_string_conversions.h"
#include "brightray/browser/browser_client.h"
#include "brightray/browser/notification.h"
#include "brightray/browser/notification_delegate.h"
#include "brightray/browser/notification_presenter.h"
#include "content/public/browser/notification_event_dispatcher.h"
#include "content/public/common/notification_resources.h"
#include "content/public/common/platform_notification_data.h"
#include "third_party/skia/include/core/SkBitmap.h"
namespace brightray {
namespace {
void OnWebNotificationAllowed(base::WeakPtr<Notification> notification,