Examine source code of High Contrast Mode

{
  "manifest_version": 2,
  "name": "High Contrast Mode",
  "version": "1.0",
  "description": "Boost color contrast for better readability.",
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "browser_action": {
    "default_title": "High Contrast Mode",
    "default_popup": "popup.html"
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{683652f1-1974-4b89-a070-8128e81f0511}"
    }
  }
}