Examine source code of Briefly (TAB In Frame)

{
  "manifest_version": 2,
  "name": "Briefly",
  "version": "1.0.1",
  "description": "Preview links in a floating frame on hover.",
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "content.css"
      ],
      "all_frames": true
    }
  ],
  "permissions": [
    "<all_urls>",
    "webRequest",
    "webRequestBlocking",
    "activeTab",
    "storage"
  ],
  "browser_action": {
    "default_popup": "popup/popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{35c205ff-a14c-40ca-923f-8df20974346b}"
    }
  }
}