Examine source code of Water Usage Tip

{
  "manifest_version": 2,
  "name": "Water Usage Tip",
  "version": "1.0",
  "description": "Shows a daily water-saving tip on each new tab.",
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  },
  "permissions": [],
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{523f6a81-c723-4847-8446-ab565e077e72}"
    }
  }
}