Push API: define push event on Service Worker.

Source/modules/modules.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
     # ways.
     'extra_blink_module_idl_files': [],
     'extra_blink_module_files': [],
     # Files for which bindings (.cpp and .h files) will be generated
@@ skipping 85 matching lines @@
       'mediastream/RTCPeerConnection.idl',
       'mediastream/RTCSessionDescription.idl',
       'mediastream/RTCSessionDescriptionCallback.idl',
       'mediastream/RTCStatsCallback.idl',
       'mediastream/RTCStatsReport.idl',
       'mediastream/RTCStatsResponse.idl',
       'mediastream/SourceInfo.idl',
       'notifications/Notification.idl',
       'notifications/NotificationPermissionCallback.idl',
       'performance/WorkerPerformance.idl',
+      'push_messaging/PushEvent.idl',
       'push_messaging/PushManager.idl',
       'push_messaging/PushRegistration.idl',
       'quota/DeprecatedStorageInfo.idl',
       'quota/DeprecatedStorageQuota.idl',
       'quota/StorageErrorCallback.idl',
       'quota/StorageInfo.idl',
       'quota/StorageQuota.idl',
       'quota/StorageQuotaCallback.idl',
       'quota/StorageUsageCallback.idl',
       'serviceworkers/Cache.idl',
@@ skipping 121 matching lines @@
       'device_orientation/DeviceOrientationEvent.idl',
       'encryptedmedia/MediaKeyMessageEvent.idl',
       'encryptedmedia/MediaKeyNeededEvent.idl',
       'gamepad/GamepadEvent.idl',
       'indexeddb/IDBVersionChangeEvent.idl',
       'mediastream/MediaStreamEvent.idl',
       'mediastream/MediaStreamTrackEvent.idl',
       'mediastream/RTCDTMFToneChangeEvent.idl',
       'mediastream/RTCDataChannelEvent.idl',
       'mediastream/RTCIceCandidateEvent.idl',
+      'push_messaging/PushEvent.idl',
       'serviceworkers/FetchEvent.idl',
       'serviceworkers/InstallEvent.idl',
       'serviceworkers/InstallPhaseEvent.idl',
       'speech/SpeechRecognitionError.idl',
       'speech/SpeechRecognitionEvent.idl',
       'speech/SpeechSynthesisEvent.idl',
       'webaudio/AudioProcessingEvent.idl',
       'webaudio/OfflineAudioCompletionEvent.idl',
       'webmidi/MIDIConnectionEvent.idl',
       'webmidi/MIDIMessageEvent.idl',
@@ skipping 315 matching lines @@
       'performance/WorkerGlobalScopePerformance.cpp',
       'performance/WorkerGlobalScopePerformance.h',
       'performance/WorkerPerformance.cpp',
       'performance/WorkerPerformance.h',
       'push_messaging/NavigatorPushManager.cpp',
       'push_messaging/NavigatorPushManager.h',
       'push_messaging/PushController.cpp',
       'push_messaging/PushController.h',
       'push_messaging/PushError.cpp',
       'push_messaging/PushError.h',
+      'push_messaging/PushEvent.cpp',
+      'push_messaging/PushEvent.h',
       'push_messaging/PushManager.cpp',
       'push_messaging/PushManager.h',
       'push_messaging/PushRegistration.cpp',
       'push_messaging/PushRegistration.h',
       'quota/DOMWindowQuota.cpp',
       'quota/DOMWindowQuota.h',
       'quota/DeprecatedStorageInfo.cpp',
       'quota/DeprecatedStorageInfo.h',
       'quota/DeprecatedStorageQuota.cpp',
       'quota/DeprecatedStorageQuota.h',
@@ skipping 335 matching lines @@
       'indexeddb/IDBKeyPathTest.cpp',
       'indexeddb/IDBRequestTest.cpp',
       'indexeddb/IDBTransactionTest.cpp',
       'websockets/WebSocketDeflaterTest.cpp',
       'websockets/WebSocketExtensionDispatcherTest.cpp',
       'websockets/WebSocketExtensionParserTest.cpp',
       'websockets/WebSocketPerMessageDeflateTest.cpp',
     ],
   },
 }