Examine source code of Text Size Changer

{
  "manifest_version": 2,
  "name": "Text Size Changer",
  "description": "This extension allows you to change the text size on websites.",
  "version": "1.0",
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icons/icon48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{78494894-95d9-4d39-89ed-d9c266a1a73d}"
    }
  }
}