chromium/chrome/test/data/chromedriver/all_frames/manifest.json

{
  "manifest_version": 2,
  "name": "All Frames",
  "description": "An extension with a content script that runs in all frames",
  "version": "1.0",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_start",
      "js": [
        "document_start.js"
      ],
      "all_frames": true
    }
  ],
  "permissions": [
    "<all_urls>"
  ]
}