Examine source code of Focusly: Active & Focused Tabs

{
  "manifest_version": 2,
  "name": "Focusly: Active & Focused Tabs",
  "description": "Browser extension that keeps configured tabs focused/active even when they are not in the foreground.",
  "version": "1.0.2",
  "icons": {
    "16": "icon/enabled/16.png",
    "32": "icon/enabled/32.png",
    "48": "icon/enabled/48.png",
    "96": "icon/enabled/96.png",
    "128": "icon/enabled/128.png"
  },
  "permissions": [
    "storage",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Default Popup Title",
    "default_popup": "popup.html"
  },
  "options_ui": {
    "open_in_tab": true,
    "page": "options.html"
  },
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "all_frames": true,
      "run_at": "document_start",
      "js": [
        "content-scripts/isolated-world.js"
      ],
      "match_origin_as_fallback": true,
      "world": "ISOLATED"
    },
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "all_frames": true,
      "run_at": "document_start",
      "js": [
        "content-scripts/main-world.js"
      ],
      "match_origin_as_fallback": true,
      "world": "MAIN"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{791144e8-5602-432b-94e4-046a4770c111}"
    }
  }
}