DevTools: do not add paint profiler tab more than once on Layers panel

third_party/WebKit/Source/devtools/front_end/layers/LayersPanel.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 138 matching lines @@
 
   /**
    * @param {!Common.Event} event
    */
   _onPaintProfileRequested(event) {
     var selection = /** @type {!LayerViewer.LayerView.Selection} */ (event.data);
     this._layers3DView.snapshotForSelection(selection).then(snapshotWithRect => {
       if (!snapshotWithRect)
         return;
       this._layerBeingProfiled = selection.layer();
-      this._tabbedPane.appendTab(
-          Layers.LayersPanel.DetailsViewTabs.Profiler, Common.UIString('Profiler'), this._paintProfilerView, undefined,
-          true, true);
+      if (!this._tabbedPane.hasTab(Layers.LayersPanel.DetailsViewTabs.Profiler)) {
+        this._tabbedPane.appendTab(
+            Layers.LayersPanel.DetailsViewTabs.Profiler, Common.UIString('Profiler'), this._paintProfilerView,
+            undefined, true, true);
+      }
       this._tabbedPane.selectTab(Layers.LayersPanel.DetailsViewTabs.Profiler);
       this._paintProfilerView.profile(snapshotWithRect.snapshot);
     });
   }
 
   /**
    * @param {!Common.Event} event
    */
   _onTabClosed(event) {
     if (event.data.tabId !== Layers.LayersPanel.DetailsViewTabs.Profiler || !this._layerBeingProfiled)
@@ skipping 15 matching lines @@
    */
   _onScaleChanged(event) {
     this._paintProfilerView.setScale(/** @type {number} */ (event.data));
   }
 };
 
 Layers.LayersPanel.DetailsViewTabs = {
   Details: 'details',
   Profiler: 'profiler'
 };