DevTools: Unify main thread name across vanilla and tracing timeline modes.

Source/devtools/front_end/timeline/TimelineFrameModel.js

 /*
  * Copyright (C) 2013 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 257 matching lines @@
             if (!this._aggregatedMainThreadWork && this._findRecordRecursively(WebInspector.TimelineFrameModel._mainFrameMarkers, programRecord))
                 this._aggregatedMainThreadWork = {};
         }
         /** type {Array.<!WebInspector.TimelineModel.Record>} */
         var records = [];
         if (!this._mergeRecords)
             records = [record];
         else
             records = this._mergingBuffer.process(record.thread(), /** type {Array.<!WebInspector.TimelineModel.Record>} */(programRecord ? record.children() || [] : [record]));
         for (var i = 0; i < records.length; ++i) {
-            if (records[i].thread())
+            if (records[i].thread() === WebInspector.TimelineModel.MainThreadName)
+                this._addMainThreadRecord(programRecord, records[i]);
+            else
                 this._addBackgroundRecord(records[i]);
-            else
-                this._addMainThreadRecord(programRecord, records[i]);
         }
     },
 
     /**
      * @param {!WebInspector.TimelineModel.Record} record
      */
     _addBackgroundRecord: function(record)
     {
         var recordTypes = WebInspector.TimelineModel.RecordType;
         if (record.type() === recordTypes.BeginFrame)
@@ skipping 278 matching lines @@
     /**
      * @param {string} category
      * @param {number} time
      */
     _addTimeForCategory: function(category, time)
     {
         this.timeByCategory[category] = (this.timeByCategory[category] || 0) + time;
         this.cpuTime += time;
     },
 }