Examine source code of HTTP Headers Viewer

{
  "manifest_version": 2,
  "name": "HTTP Headers Viewer",
  "version": "1.0",
  "description": "Displays HTTP response headers for the current tab.",
  "icons": {
    "64": "icons/icon64.png",
    "128": "icons/icon128.png"
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/icon64.png",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{af821333-0d9a-4ea5-a20c-efa7766d56b9}",
      "strict_min_version": "120.0"
    }
  }
}