Examine source code of OpenThisUrl

{
  "manifest_version": 2,
  "name": "OpenThisUrl",
  "version": "1.0.2",
  "description": "Send links from your desktop/laptop to your mobile.",
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "browser_action": {
    "default_icon": "icons/openthisurl.png",
    "default_title": "OpenThisUrl",
    "default_popup": "popup/popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "popup/popup.js"
      ]
    }
  ]
}