Examine source code of Google Similar Sites

{
  "name": "__MSG_extName__",
  "description": "__MSG_extDesc__",
  "version": "1.0.0",
  "manifest_version": 2,
  "default_locale": "en",
  "browser_action": {
    "default_icon": {
      "16": "build/logo_16.png",
      "24": "build/logo_24.png",
      "32": "build/logo_32.png"
    }
  },
  "icons": {
    "16": "build/logo_16.png",
    "48": "build/logo_48.png",
    "128": "build/logo_128.png"
  },
  "web_accessible_resources": [
    "build/*"
  ],
  "background": {
    "scripts": [
      "build/browser-polyfill.js",
      "build/background.js"
    ]
  },
  "permissions": [
    "tabs"
  ]
}