Examine source code of WebTime - Time Tracker

{
  "manifest_version": 2,
  "name": "Web Time",
  "version": "0.5.5",
  "description": "Track and take control of the time you spend on the web",
  "permissions": [
    "tabs",
    "<all_urls>",
    "storage"
  ],
  "browser_action": {
    "default_icon": {
      "128": "icon128.png"
    },
    "default_title": "Web Time",
    "default_popup": "popup/popup.html"
  },
  "icons": {
    "128": "icon128.png"
  },
  "background": {
    "scripts": [
      "shared/constants.js",
      "shared/utils.js",
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "shared/constants.js",
        "shared/utils.js",
        "content.js"
      ],
      "css": [
        "timer.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "webtime@somedomain.com"
    }
  }
}