Support performance.now() in workers.

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': [],
 
@@ skipping 85 matching lines @@
       'mediastream/RTCStatsCallback.idl',
       'mediastream/RTCStatsReport.idl',
       'mediastream/RTCStatsResponse.idl',
       'mediastream/SourceInfo.idl',
       'navigatorcontentutils/NavigatorContentUtils.idl',
       'notifications/DOMWindowNotifications.idl',
       'notifications/Notification.idl',
       'notifications/NotificationCenter.idl',
       'notifications/NotificationPermissionCallback.idl',
       'notifications/WorkerContextNotifications.idl',
+      'performance/WorkerContextPerformance.idl',
+      'performance/WorkerPerformance.idl',
       'quota/DOMWindowQuota.idl',
       'quota/NavigatorStorageQuota.idl',
       'quota/StorageErrorCallback.idl',
       'quota/StorageInfo.idl',
       'quota/StorageQuota.idl',
       'quota/StorageQuotaCallback.idl',
       'quota/StorageUsageCallback.idl',
       'quota/WorkerNavigatorStorageQuota.idl',
       'speech/DOMWindowSpeechSynthesis.idl',
       'speech/SpeechGrammar.idl',
@@ skipping 296 matching lines @@
       'notifications/DOMWindowNotifications.h',
       'notifications/Notification.cpp',
       'notifications/Notification.h',
       'notifications/NotificationCenter.cpp',
       'notifications/NotificationCenter.h',
       'notifications/NotificationController.cpp',
       'notifications/NotificationController.h',
       'notifications/NotificationPermissionCallback.h',
       'notifications/WorkerContextNotifications.cpp',
       'notifications/WorkerContextNotifications.h',
+      'performance/WorkerContextPerformance.cpp',
+      'performance/WorkerContextPerformance.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',
       'quota/StorageErrorCallback.cpp',
       'quota/StorageErrorCallback.h',
       'quota/StorageQuota.cpp',
       'quota/StorageQuota.h',
@@ skipping 237 matching lines @@
       'websockets/WorkerThreadableWebSocketChannel.cpp',
       'websockets/WorkerThreadableWebSocketChannel.h',
     ],
     'modules_unittest_files': [
       'websockets/WebSocketDeflaterTest.cpp',
       'websockets/WebSocketExtensionDispatcherTest.cpp',
       'websockets/WebSocketPerMessageDeflateTest.cpp',
     ],
   },
 }