Is there a way to ascertain the summary data from a timeline trace JSON file from Chrome Dev Tools?

[Ed Prince]

As I understand it, those figures are being generated dynamically, so they won't exist in the JSON file, but can be calculated - but I have no idea where to start. The objects have categories - but they don't match up to these subheadings, instead are:

• toplevel
• devtools.timeline
• _metadata
• benchmark,latencyInfo,rail
• base,toplevel
• disabled-by-default-v8.cpu_profiler
• disabled-by-default-devtools.timeline.frame

(and probably a few more I have missed)
Here is an example object:

{
  "pid":11032,
  "tid":8628,
  "ts":14748132182,
  "ph":"X",
  "cat":"toplevel",
  "name":"ThreadController::Task",
  "args": { 
    "src_file":"../../content/browser/devtools/devtools_http_handler.cc",
    "src_func":"DispatchProtocolMessage"
  },
  "dur":208,
  "tdur":187,
  "tts":29121
}