sample.log

{
  "threads": [
    {
      "name" : "Main Thread",
      "samples": [
        {
          "name": "(root)",
          "frames": [
            {
              "location": "Main"
            },
            {
              "location": "Process Event"
            },
            {
              "location": "js_mozilla() (in mozilla.com)"
            }
          ]
        },
        {
          "name": "(root)",
          "frames": [
            {
              "location": "Main"
            },
            {
              "location": "Process Event"
            },
            {
              "location": "onclick (in XUL)"
            }
          ]
        }
      ]
    }
  ]
}