DevTools Timeline: fix NPE when collapsing the last group

third_party/WebKit/Source/devtools/front_end/perf_ui/FlameChart.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 335 matching lines @@
     this._groupExpansionState[group.name] = group.expanded;
     if (this._groupExpansionSetting)
       this._groupExpansionSetting.set(this._groupExpansionState);
     this._updateLevelPositions();
 
     this._updateHighlight();
     if (!group.expanded) {
       var timelineData = this._timelineData();
       var level = timelineData.entryLevels[this._selectedEntryIndex];
       if (this._selectedEntryIndex >= 0 && level >= group.startLevel &&
-          (groupIndex === groups.length || groups[groupIndex + 1].startLevel > level))
+          (groupIndex >= groups.length - 1 || groups[groupIndex + 1].startLevel > level))
         this._selectedEntryIndex = -1;
     }
 
     this._updateHeight();
     this._resetCanvas();
     this._draw(this._offsetWidth, this._offsetHeight);
   }
 
   /**
    * @param {!Event} e
@@ skipping 1162 matching lines @@
   }
 
   /**
    * @override
    * @return {number}
    */
   boundarySpan() {
     return this._maximumBoundaries - this._minimumBoundaries;
   }
 };