Examine source code of KeywordDensityChecker

{
  "manifest_version": 2,
  "name": "KeywordDensityChecker",
  "version": "1.2",
  "description": "Check keyword density on the current webpage.",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6719394f-863f-454b-99fe-c188491c3188}"
    }
  }
}