Examine source code of Mirror

{
  "manifest_version": 2,
  "name": "Mirror",
  "description": "This mirror flips your online activity!",
  "version": "1.1resigned1",
  "author": "joak",
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html",
    "default_title": "Flip horizontally page!",
    "browser_style": false
  },
  "icons": {
    "16": "icon-16.png",
    "32": "icon-32.png",
    "64": "icon-64.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e88253ef-089e-4b36-b2a9-a0735958c62f}"
    }
  }
}