Examine source code of Composition Grid

{
  "manifest_version": 2,
  "name": "Composition Grid",
  "version": "1.0",
  "description": "Toggle between thirds and golden ratio grids on any webpage.",
  "permissions": [
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_icon": {
      "64": "icons/grid_off_64.png"
    },
    "default_title": "Composition Grid"
  },
  "icons": {
    "64": "icons/grid_off_64.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{af9de968-eac2-400a-9cd5-4a4ff0a60863}"
    }
  }
}