Examine source code of FontSizer

{
  "manifest_version": 2,
  "name": "FontSizer",
  "version": "1.0",
  "description": "Extension to change font size on web pages",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    },
    "default_title": "FontSizer",
    "default_popup": "popup/popup.html"
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_script.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{2adace5d-747f-41b0-a937-1c0de8010353}"
    }
  }
}