Examine source code of Timer Pie Chart

{
  "manifest_version": 2,
  "name": "Timer Pie Chart",
  "version": "1.0.2",
  "description": "Adds a pie chart to the default timer on Google",
  "icons": {
    "48": "icons/48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.google.com/*"
      ],
      "js": [
        "modifyTimer.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{7c476bd5-c1f2-43b4-b4d1-2962816a0522}"
    }
  }
}