Environment warning

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "name": "Environment warning",
  "description": "This extension will show a warning for selected environment/URL",
  "version": "1.0",
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "default_icon": "images/icon.png",
    "default_title": "Environment Warning",
    "default_popup": "popup.html"
  },
  "icons": {
    "16": "images/icon_16.png",
    "48": "images/icon_48.png",
    "128": "images/icon_128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "run_at": "document_start",
      "js": [
        "showWarning.js"
      ]
    }
  ],
  "incognito": "spanning",
  "web_accessible_resources": [
    "images/*.png"
  ],
  "content_security_policy": "script-src 'self' https://apis.google.com; object-src 'self'"
}