Start to implement FetchEvent for ServiceWorker

Source/web/web.gypi

 {
   'variables': {
     'web_files': [
       'AssertMatchingEnums.cpp',
       'AssociatedURLLoader.cpp',
       'AssociatedURLLoader.h',
       'BackForwardClientImpl.cpp',
       'BackForwardClientImpl.h',
       'ChromeClientImpl.cpp',
       'ChromeClientImpl.h',
@@ skipping 207 matching lines @@
       'WebScopedWindowFocusAllowedIndicator.cpp',
       'WebScriptBindings.cpp',
       'WebScriptController.cpp',
       'WebScrollbarThemePainter.cpp',
       'WebSearchableFormData.cpp',
       'WebSecurityOrigin.cpp',
       'WebSecurityPolicy.cpp',
       'WebSelectElement.cpp',
       'WebSelector.cpp',
       'WebSerializedScriptValue.cpp',
+      'WebServiceWorkerFetchResponse.cpp',
       'WebSettingsImpl.cpp',
       'WebSettingsImpl.h',
       'WebSharedWorkerImpl.cpp',
       'WebSharedWorkerImpl.h',
       'WebSocket.cpp',
       'WebSocketImpl.cpp',
       'WebSocketImpl.h',
       'WebSpeechGrammar.cpp',
       'WebSpeechInputResult.cpp',
       'WebSpeechRecognitionHandle.cpp',
@@ skipping 128 matching lines @@
         {
           'web_unittest_files': [
             'tests/KeyCodeConversionTestGtk.cpp',
             'tests/WebInputEventFactoryTestGtk.cpp',
           ],
         }
       ],
     ],
   },
 }