DevTools: Show screenshots on the main flamechart

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
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    */
   _isGroupCollapsible(index) {
     var groups = this._rawTimelineData.groups || [];
     var style = groups[index].style;
     if (!style.shareHeaderLine || !style.collapsible)
       return !!style.collapsible;
     var isLastGroup = index + 1 >= groups.length;
     if (!isLastGroup && groups[index + 1].style.nestingLevel > style.nestingLevel)
       return true;
     var nextGroupLevel = isLastGroup ? this._dataProvider.maxStackDepth() : groups[index + 1].startLevel;
-    // For groups that only have one line and share header line, pretend these are not collapsible.
-    return nextGroupLevel !== groups[index].startLevel + 1;
+    if (nextGroupLevel !== groups[index].startLevel + 1)
+      return true;
+    // For groups that only have one line and share header line, pretend these are not collapsible
+    // unless the itemsHeight does not match the headerHeight
+    return style.height !== style.itemsHeight;
   }
 
   /**
    * @param {number} entryIndex
    */
   setSelectedEntry(entryIndex) {
     if (entryIndex === -1 && !this.isDragging())
       this.hideRangeSelection();
     if (this._selectedEntryIndex === entryIndex)
       return;
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   }
 
   /**
    * @override
    * @return {number}
    */
   boundarySpan() {
     return this._maximumBoundaries - this._minimumBoundaries;
   }
 };