Timeline: fix exception when clicking on drawer padding with collapsible groups enabled

third_party/WebKit/Source/devtools/front_end/ui_lazy/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 1096 matching lines @@
      * @return {number}
      */
     _coordinatesToGroupIndex: function(x, y)
     {
         if (x < 0 || y < 0)
             return -1;
         y += this._scrollTop;
         var groups = this._rawTimelineData.groups || [];
         var group = this._groupOffsets.upperBound(y) - 1;
 
-        if (group >= 0 && y - this._groupOffsets[group] < groups[group].style.height)
+        if (group >= 0 && group < groups.length && y - this._groupOffsets[group] < groups[group].style.height)
             return group;
         return -1;
     },
 
     /**
      * @param {number} x
      * @return {number}
      */
     _markerIndexAtPosition: function(x)
     {
@@ skipping 198 matching lines @@
      * @param {number} height
      */
     _drawGroupHeaders: function(width, height)
     {
         var context = this._canvas.getContext("2d");
         var top = this._scrollTop;
         var ratio = window.devicePixelRatio;
         var barHeight = this._barHeight;
         var textBaseHeight = barHeight - this._dataProvider.textBaseline();
         var groups = this._rawTimelineData.groups || [];
+        if (!groups.length)
+            return;
+
         var groupOffsets = this._groupOffsets;
         var lastGroupOffset = Array.prototype.peekLast.call(groupOffsets);
-
         var firstVisibleGroup = Math.max(groupOffsets.upperBound(top) - 1, 0);
 
         context.save();
         context.scale(ratio, ratio);
         context.translate(0, -top);
 
         context.fillStyle = "#eee";
         forEachGroup((offset, index, group) => {
             var paddingHeight = group.style.padding;
             if (paddingHeight < 5)
@@ skipping 616 matching lines @@
         this.update();
     },
 
     _enabled: function()
     {
         return this._rawTimelineDataLength !== 0;
     },
 
     __proto__: WebInspector.HBox.prototype
 }