Examine source code of React Performance Devtool

{
  "manifest_version": 2,
  "name": "React Performance Devtool",
  "short_name": "react-perf-devtool",
  "description": "A devtool extension for inspecting the performance of React components.",
  "version": "5resigned1",
  "devtools_page": "devtools.html",
  "icons": {
    "16": "./icon/RP16.png",
    "48": "./icon/RP48.png",
    "128": "./icon/RP128.png"
  },
  "permissions": [
    "file:///*",
    "http://*/*",
    "https://*/*"
  ],
  "content_security_policy": "script-src 'self' 'unsafe-eval'; object-src 'self'",
  "browser_specific_settings": {
    "gecko": {
      "id": "{bab76fc8-0ef8-42f8-a8d2-934bfe0fcaeb}"
    }
  }
}