Add an Error class for ServiceWorkers

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': [],
     'modules_idl_files': [
@@ skipping 497 matching lines @@
       'quota/StorageQuota.cpp',
       'quota/StorageQuota.h',
       'quota/StorageQuotaCallback.h',
       'quota/StorageUsageCallback.h',
       'quota/WebStorageQuotaCallbacksImpl.cpp',
       'quota/WebStorageQuotaCallbacksImpl.h',
       'quota/WorkerNavigatorStorageQuota.cpp',
       'quota/WorkerNavigatorStorageQuota.h',
       'serviceworkers/ServiceWorker.cpp',
       'serviceworkers/ServiceWorker.h',
+      'serviceworkers/ServiceWorkerError.cpp',
+      'serviceworkers/ServiceWorkerError.h',
       'serviceworkers/NavigatorServiceWorker.cpp',
       'serviceworkers/NavigatorServiceWorker.h',
       'speech/DOMWindowSpeechSynthesis.cpp',
       'speech/DOMWindowSpeechSynthesis.h',
       'speech/SpeechGrammar.cpp',
       'speech/SpeechGrammar.h',
       'speech/SpeechGrammarList.cpp',
       'speech/SpeechGrammarList.h',
       'speech/SpeechRecognition.cpp',
       'speech/SpeechRecognition.h',
@@ skipping 259 matching lines @@
       'indexeddb/IDBKeyPathTest.cpp',
       'indexeddb/IDBRequestTest.cpp',
       'indexeddb/IDBTransactionTest.cpp',
       'websockets/WebSocketDeflaterTest.cpp',
       'websockets/WebSocketExtensionDispatcherTest.cpp',
       'websockets/WebSocketExtensionParserTest.cpp',
       'websockets/WebSocketPerMessageDeflateTest.cpp',
     ],
   },
 }