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

Source/devtools/front_end/timeline/TimelineView.js

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  * Copyright (C) 2012 Intel 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.
@@ skipping 1049 matching lines @@
         this._record = presentationRecord;
         var record = presentationRecord.record();
         this._offset = offset;
 
         this.element.className = "timeline-tree-item timeline-category-" + uiUtils.categoryForRecord(record).name;
         var paddingLeft = 5;
         var step = -3;
         for (var currentRecord = presentationRecord.presentationParent() ? presentationRecord.presentationParent().presentationParent() : null; currentRecord; currentRecord = currentRecord.presentationParent())
             paddingLeft += 12 / (Math.max(1, step++));
         this.element.style.paddingLeft = paddingLeft + "px";
-        if (record.thread() && record.thread() !== "CPU")
+        if (record.thread() !== WebInspector.TimelineModel.MainThreadName)
             this.element.classList.add("background");
 
         this._typeElement.textContent = uiUtils.titleForRecord(record);
 
         if (this._dataElement.firstChild)
             this._dataElement.removeChildren();
 
         this._warningElement.classList.toggle("hidden", !presentationRecord.hasWarnings() && !presentationRecord.childHasWarnings());
         this._warningElement.classList.toggle("timeline-tree-item-child-warning", presentationRecord.childHasWarnings() && !presentationRecord.hasWarnings());
 
@@ skipping 106 matching lines @@
      * @param {!WebInspector.TimelineCalculator} calculator
      * @param {number} expandOffset
      * @param {number} index
      * @param {!WebInspector.TimelineUIUtils} uiUtils
      */
     update: function(presentationRecord, calculator, expandOffset, index, uiUtils)
     {
         this._record = presentationRecord;
         var record = presentationRecord.record();
         this.element.className = "timeline-graph-side timeline-category-" + uiUtils.categoryForRecord(record).name;
-        if (record.thread() && record.thread() !== "CPU")
+        if (record.thread() !== WebInspector.TimelineModel.MainThreadName)
             this.element.classList.add("background");
 
         var barPosition = calculator.computeBarGraphWindowPosition(presentationRecord);
         this._barElement.style.left = barPosition.left + "px";
         this._barElement.style.width = barPosition.width + "px";
         this._barCpuElement.style.left = barPosition.left + "px";
         this._barCpuElement.style.width = barPosition.cpuWidth + "px";
         this._expandElement._update(presentationRecord, index, barPosition.left - expandOffset, barPosition.width);
         this._record.setGraphRow(this);
     },
@@ skipping 87 matching lines @@
         } else {
             this._element.classList.add("hidden");
         }
     },
 
     _dispose: function()
     {
         this._element.remove();
     }
 }