Examine source code of Download Deleter

{
  "description": "__MSG_extensionDescription__",
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "version": "1.0",
  "icons": {
    "32": "icons/logo_32.png",
    "64": "icons/logo_64.png",
    "128": "icons/logo_128.png"
  },
  "permissions": [
    "downloads",
    "downloads.open"
  ],
  "browser_action": {
    "browser_style": true,
    "default_icon": "icons/logo_64.png",
    "default_title": "Delete Last Download",
    "default_popup": "popup/download.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{7cfb6f43-626f-4af9-b8ba-b35af872cb5e}"
    }
  }
}