Examine source code of Mood Color Picker

{
  "manifest_version": 2,
  "name": "Mood Color Picker",
  "version": "1.0",
  "description": "Displays a color corresponding to your mood.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_popup": "index.html"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ba153a42-f14c-48e7-99a2-3078190fce51}"
    }
  }
}