Examine source code of Circle Screenshot

{
  "name": "__MSG_name__",
  "version": "1.1.2",
  "manifest_version": 2,
  "description": "__MSG_description__",
  "background": {
    "scripts": [
      "worker.js"
    ],
    "persistent": true
  },
  "permissions": [
    "contextMenus",
    "<all_urls>"
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "icons": {
    "16": "icons/16.png",
    "32": "icons/32.png",
    "48": "icons/48.png",
    "128": "icons/128.png"
  },
  "default_locale": "en",
  "options_ui": {
    "page": "option.html",
    "open_in_tab": true
  },
  "homepage_url": "http://circlereader.com/screenshot",
  "content_scripts": [
    {
      "js": [
        "app.js"
      ],
      "all_frames": false,
      "run_at": "document_start",
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "web_accessible_resources": [
    "widget/*.css"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{84cb69fe-952a-4c83-a685-0d067848f863}"
    }
  }
}