Introduce the NotificationEvent object.

Source/modules/modules.gypi

 {
   'includes': [
     '../core/core_generated.gypi',
     'modules_generated.gypi',
   ],
   'variables': {
     # Experimental hooks for embedder to provide extra IDL and source files.
     #
     # Note: this is not a supported API. If you rely on this, you will be broken
     # from time to time as the code generator changes in backward incompatible
@@ skipping 96 matching lines @@
       'mediastream/RTCIceCandidateEvent.idl',
       'mediastream/RTCPeerConnection.idl',
       'mediastream/RTCSessionDescription.idl',
       'mediastream/RTCSessionDescriptionCallback.idl',
       'mediastream/RTCStatsCallback.idl',
       'mediastream/RTCStatsReport.idl',
       'mediastream/RTCStatsResponse.idl',
       'mediastream/SourceInfo.idl',
       'netinfo/NetworkInformation.idl',
       'notifications/Notification.idl',
+      'notifications/NotificationEvent.idl',
       'notifications/NotificationPermissionCallback.idl',
       'performance/WorkerPerformance.idl',
       'presentation/Presentation.idl',
       'presentation/PresentationSession.idl',
       'push_messaging/PushEvent.idl',
       'push_messaging/PushManager.idl',
       'push_messaging/PushRegistration.idl',
       'quota/DeprecatedStorageInfo.idl',
       'quota/DeprecatedStorageQuota.idl',
       'quota/StorageErrorCallback.idl',
@@ skipping 139 matching lines @@
       'encryptedmedia/MediaEncryptedEvent.idl',
       'encryptedmedia/MediaKeyMessageEvent.idl',
       'gamepad/GamepadEvent.idl',
       'geofencing/GeofencingEvent.idl',
       'indexeddb/IDBVersionChangeEvent.idl',
       'mediastream/MediaStreamEvent.idl',
       'mediastream/MediaStreamTrackEvent.idl',
       'mediastream/RTCDTMFToneChangeEvent.idl',
       'mediastream/RTCDataChannelEvent.idl',
       'mediastream/RTCIceCandidateEvent.idl',
+      'notifications/NotificationEvent.idl',
       'push_messaging/PushEvent.idl',
       'serviceworkers/ExtendableEvent.idl',
       'serviceworkers/FetchEvent.idl',
       'serviceworkers/InstallEvent.idl',
       'speech/SpeechRecognitionError.idl',
       'speech/SpeechRecognitionEvent.idl',
       'speech/SpeechSynthesisEvent.idl',
       'webaudio/AudioProcessingEvent.idl',
       'webaudio/OfflineAudioCompletionEvent.idl',
       'webmidi/MIDIConnectionEvent.idl',
@@ skipping 443 matching lines @@
       'netinfo/NavigatorNetworkInformation.h',
       'netinfo/NetworkInformation.cpp',
       'netinfo/NetworkInformation.h',
       'netinfo/WorkerNavigatorNetworkInformation.cpp',
       'netinfo/WorkerNavigatorNetworkInformation.h',
       'notifications/Notification.cpp',
       'notifications/Notification.h',
       'notifications/NotificationClient.h',
       'notifications/NotificationController.cpp',
       'notifications/NotificationController.h',
+      'notifications/NotificationEvent.cpp',
+      'notifications/NotificationEvent.h',
       'notifications/NotificationPermissionCallback.h',
       'notifications/NotificationPermissionClient.cpp',
       'notifications/NotificationPermissionClient.h',
       'performance/SharedWorkerPerformance.cpp',
       'performance/WorkerGlobalScopePerformance.cpp',
       'performance/WorkerGlobalScopePerformance.h',
       'performance/WorkerPerformance.cpp',
       'performance/WorkerPerformance.h',
       'presentation/NavigatorPresentation.cpp',
       'presentation/NavigatorPresentation.h',
@@ skipping 362 matching lines @@
       'serviceworkers/CacheTest.cpp',
       'serviceworkers/FetchResponseDataTest.cpp',
       'serviceworkers/RequestTest.cpp',
       'serviceworkers/ResponseTest.cpp',
       'serviceworkers/ServiceWorkerContainerTest.cpp',
       'websockets/DOMWebSocketTest.cpp',
       'websockets/DocumentWebSocketChannelTest.cpp',
     ],
   },
 }