Examine source code of Scroll by PX

{
  "manifest_version": 2,
  "name": "Scroll by PX",
  "version": "1.0",
  "description": "Scroll the page by specified px.",
  "homepage_url": "https://github.com/chho/scroll_px_extension",
  "icons": {
    "48": "icons/px_icon_48.png",
    "96": "icons/px_icon_96.png"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "browser_action": {
    "default_icon": "icons/px_icon_32.png",
    "default_title": "Scroll by PX",
    "default_popup": "popup/scroll_px.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c6da46ec-d69d-4806-af22-f5dd04657f52}"
    }
  }
}