Add the SharedWorker.workerStart property for high resolution timers.

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 107 matching lines @@
       'mediastream/RTCStatsResponse.idl',
       'mediastream/SourceInfo.idl',
       'mediastream/URLMediaStream.idl',
       'navigatorcontentutils/NavigatorContentUtils.idl',
       'notifications/Notification.idl',
       'notifications/NotificationCenter.idl',
       'notifications/NotificationPermissionCallback.idl',
       'notifications/WebKitNotification.idl',
       'notifications/WindowNotifications.idl',
       'notifications/WorkerGlobalScopeNotifications.idl',
+      'performance/SharedWorkerPerformance.idl',
       'performance/WorkerGlobalScopePerformance.idl',
       'performance/WorkerPerformance.idl',
       'quota/NavigatorStorageQuota.idl',
       'quota/StorageErrorCallback.idl',
       'quota/StorageInfo.idl',
       'quota/StorageQuota.idl',
       'quota/StorageQuotaCallback.idl',
       'quota/StorageUsageCallback.idl',
       'quota/WindowQuota.idl',
       'quota/WorkerNavigatorStorageQuota.idl',
@@ skipping 363 matching lines @@
       'notifications/NotificationBase.h',
       'notifications/NotificationCenter.cpp',
       'notifications/NotificationCenter.h',
       'notifications/NotificationController.cpp',
       'notifications/NotificationController.h',
       'notifications/NotificationPermissionCallback.h',
       'notifications/WebKitNotification.cpp',
       'notifications/WebKitNotification.h',
       'notifications/WorkerGlobalScopeNotifications.cpp',
       'notifications/WorkerGlobalScopeNotifications.h',
+      'performance/SharedWorkerPerformance.cpp',
       'performance/WorkerGlobalScopePerformance.cpp',
       'performance/WorkerGlobalScopePerformance.h',
       'performance/WorkerPerformance.cpp',
       'performance/WorkerPerformance.h',
       'quota/DOMWindowQuota.cpp',
       'quota/DOMWindowQuota.h',
       'quota/NavigatorStorageQuota.cpp',
       'quota/NavigatorStorageQuota.h',
       'quota/StorageInfo.cpp',
       'quota/StorageInfo.h',
@@ skipping 284 matching lines @@
       'indexeddb/IDBKeyPathTest.cpp',
       'indexeddb/IDBRequestTest.cpp',
       'indexeddb/IDBTransactionTest.cpp',
       'websockets/WebSocketDeflaterTest.cpp',
       'websockets/WebSocketExtensionDispatcherTest.cpp',
       'websockets/WebSocketExtensionParserTest.cpp',
       'websockets/WebSocketPerMessageDeflateTest.cpp',
     ],
   },
 }