Examine source code of Clear This Page

{
  "name": "Clear This Page",
  "description": "Take any web article or news page and returns only the relevant content, freeing you from any clutter.",
  "version": "1.0",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "name": "Click to extract content from the current browser tab"
  },
  "manifest_version": 2
}