ServiceWorker: Introduce ExtendableMessageEvent to replace MessageEvent

Source/modules/modules.gypi

Index: Source/modules/modules.gypi
diff --git a/Source/modules/modules.gypi b/Source/modules/modules.gypi
index 0db74fc9c7c151cbcb1ac527741c25b965f4157c..59a407a2c66c9672c8db7ab948d2268d03e75c82 100644
--- a/Source/modules/modules.gypi
+++ b/Source/modules/modules.gypi
@@ -166,6 +166,7 @@
       'serviceworkers/Client.idl',
       'serviceworkers/Clients.idl',
       'serviceworkers/ExtendableEvent.idl',
+      'serviceworkers/ExtendableMessageEvent.idl',
       'serviceworkers/FetchEvent.idl',
       'serviceworkers/ServiceWorker.idl',
       'serviceworkers/ServiceWorkerContainer.idl',
@@ -337,6 +338,7 @@
       'presentation/DefaultSessionStartEvent.idl',
       'push_messaging/PushEvent.idl',
       'serviceworkers/ExtendableEvent.idl',
+      'serviceworkers/ExtendableMessageEvent.idl',
       'serviceworkers/FetchEvent.idl',
       'serviceworkers/ServiceWorkerMessageEvent.idl',
       'speech/SpeechRecognitionError.idl',
@@ -396,6 +398,7 @@
       'push_messaging/PushSubscriptionOptions.idl',
       'serviceworkers/ClientQueryOptions.idl',
       'serviceworkers/ExtendableEventInit.idl',
+      'serviceworkers/ExtendableMessageEventInit.idl',
       'serviceworkers/FetchEventInit.idl',
       'serviceworkers/RegistrationOptions.idl',
       'serviceworkers/ServiceWorkerMessageEventInit.idl',
@@ -510,6 +513,8 @@
       '<(blink_modules_output_dir)/serviceworkers/ClientQueryOptions.h',
       '<(blink_modules_output_dir)/serviceworkers/ExtendableEventInit.cpp',
       '<(blink_modules_output_dir)/serviceworkers/ExtendableEventInit.h',
+      '<(blink_modules_output_dir)/serviceworkers/ExtendableMessageEventInit.cpp',
+      '<(blink_modules_output_dir)/serviceworkers/ExtendableMessageEventInit.h',
       '<(blink_modules_output_dir)/serviceworkers/FetchEventInit.cpp',
       '<(blink_modules_output_dir)/serviceworkers/FetchEventInit.h',
       '<(blink_modules_output_dir)/serviceworkers/RegistrationOptions.cpp',
@@ -1166,6 +1171,8 @@
       'screen_orientation/ScreenOrientationInspectorAgent.h',
       'serviceworkers/ExtendableEvent.cpp',
       'serviceworkers/ExtendableEvent.h',
+      'serviceworkers/ExtendableMessageEvent.cpp',
+      'serviceworkers/ExtendableMessageEvent.h',
       'serviceworkers/FetchEvent.cpp',
       'serviceworkers/FetchEvent.h',
       'serviceworkers/NavigatorServiceWorker.cpp',