[ServiceWorker] Support setting body to Request object in ServiceWorker.

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 686 matching lines @@
       'serviceworkers/HeadersForEachCallback.h',
       'serviceworkers/InstallEvent.cpp',
       'serviceworkers/InstallEvent.h',
       'serviceworkers/InstallPhaseEvent.cpp',
       'serviceworkers/InstallPhaseEvent.h',
       'serviceworkers/NavigatorServiceWorker.cpp',
       'serviceworkers/NavigatorServiceWorker.h',
       'serviceworkers/RegistrationOptionList.h',
       'serviceworkers/Request.cpp',
       'serviceworkers/Request.h',
+      'serviceworkers/RequestInit.cpp',
       'serviceworkers/RequestInit.h',
       'serviceworkers/RespondWithObserver.cpp',
       'serviceworkers/RespondWithObserver.h',
       'serviceworkers/Response.cpp',
       'serviceworkers/Response.h',
       'serviceworkers/ResponseInit.h',
       'serviceworkers/ServiceWorker.cpp',
       'serviceworkers/ServiceWorker.h',
       'serviceworkers/ServiceWorkerClient.cpp',
       'serviceworkers/ServiceWorkerClient.h',
@@ skipping 302 matching lines @@
       'serviceworkers/ServiceWorkerContainerTest.cpp',
       'websockets/DOMWebSocketTest.cpp',
       'websockets/NewWebSocketChannelImplTest.cpp',
       'websockets/WebSocketDeflaterTest.cpp',
       'websockets/WebSocketExtensionDispatcherTest.cpp',
       'websockets/WebSocketExtensionParserTest.cpp',
       'websockets/WebSocketPerMessageDeflateTest.cpp',
     ],
   },
 }