Examine source code of Select All Button

{
  "manifest_version": 2,
  "name": "Select All Button",
  "version": "1.0",
  "description": "Adds a button to select all text on the page.",
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "browser_action": {
    "default_icon": {
      "16": "icon-16.png",
      "32": "icon-32.png",
      "48": "icon-48.png"
    },
    "default_title": "Select All"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f2406ef5-9730-4afb-80ad-a07206d0bd31}"
    }
  }
}