Examine source code of Tweet Button

{
  "manifest_version": 2,
  "name": "Tweet Button",
  "description": "Add a tweet button to toolbar",
  "version": "2.0.1resigned1",
  "browser_action": {
    "default_icon": {
      "16": "icons/circle16.png",
      "24": "icons/circle24.png",
      "32": "icons/circle32.png",
      "48": "icons/circle48.png",
      "64": "icons/circle64.png",
      "128": "icons/circle128.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "permissions": [
    "activeTab"
  ],
  "icons": {
    "16": "icons/circle16.png",
    "24": "icons/circle24.png",
    "32": "icons/circle32.png",
    "48": "icons/circle48.png",
    "64": "icons/circle64.png",
    "128": "icons/circle128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{1a240ad5-61c4-48f1-b0e1-7df51218f8e8}"
    }
  }
}