Examine source code of Timer Extension

{
  "manifest_version": 2,
  "name": "Timer Extension",
  "version": "1.1",
  "description": "A simple timer extension for Chrome",
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "default_title": "Timer Extension",
    "default_popup": "index.html",
    "default_icon": {
      "19": "19x19.png",
      "38": "38x38.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "app.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "logo.png"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{51cefad7-4da4-4efd-888e-50f2de8035bc}"
    }
  }
}