Examine source code of SalesForce Classic View

{
  "manifest_version": 2,
  "name": "SalesForce Classic View",
  "version": "1.1",
  "description": "A simple utility to switch automatically to SalesForce classic view from ligtning view",
  "icons": {
    "48": "icon.png",
    "96": "icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.lightning.force.com/*"
      ],
      "js": [
        "mycontent_script.js"
      ]
    }
  ]
}