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

Source/devtools/front_end/timeline/TracingTimelineModel.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @constructor
  * @param {!WebInspector.TracingModel} tracingModel
  * @param {!WebInspector.TimelineModel.Filter} recordFilter
  * @extends {WebInspector.TimelineModel}
  */
@@ skipping 69 matching lines @@
     WebSocketCreate : "WebSocketCreate",
     WebSocketSendHandshakeRequest : "WebSocketSendHandshakeRequest",
     WebSocketReceiveHandshakeResponse : "WebSocketReceiveHandshakeResponse",
     WebSocketDestroy : "WebSocketDestroy",
 
     EmbedderCallback : "EmbedderCallback",
 
     CallStack: "CallStack",
     SetLayerTreeId: "SetLayerTreeId",
     TracingStartedInPage: "TracingStartedInPage",
+    TracingStartedInWorker: "TracingStartedInWorker",
 
     DecodeImage: "Decode Image",
     ResizeImage: "Resize Image",
     DrawLazyPixelRef: "Draw LazyPixelRef",
     DecodeLazyPixelRef: "Decode LazyPixelRef",
 
     LazyPixelRef: "LazyPixelRef",
     LayerTreeHostImplSnapshot: "cc::LayerTreeHostImpl",
     PictureSnapshot: "cc::Picture"
 };
@@ skipping 879 matching lines @@
     },
 
     _didWriteNextChunk: function(stream)
     {
         if (this._recordIndex === this._payloads.length)
             stream.close();
         else
             this._writeNextChunk(stream);
     }
 }