Record DevTools metadata events on worker threads when starting recoring tracing based Timeline

Source/core/workers/WorkerGlobalScopeProxy.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 46 matching lines @@
         virtual void workerObjectDestroyed() = 0;
 
         class PageInspector {
         public:
             virtual ~PageInspector() { }
             virtual void dispatchMessageFromWorker(const String&) = 0;
         };
         virtual void connectToInspector(PageInspector*) { }
         virtual void disconnectFromInspector() { }
         virtual void sendMessageToInspector(const String&) { }
+        virtual void writeTimelineStartedEvent(const String& sessionId) { }
     };
 
 } // namespace blink
 
 #endif // WorkerGlobalScopeProxy_h