Gmail Classic/Old Theme by Agile Inbox

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "name": "Gmail Classic/Old Theme by Agile Inbox",
  "version": "0.1.3.11",
  "description": "Simple extension to apply Gmail Classic/Old theme to new Gmail.",
  "icons": {
    "16": "/images/16x16.png",
    "48": "/images/48x48.png",
    "128": "/images/128x128.png"
  },
  "browser_action": {
    "default_icon": {
      "19": "/images/16x16.png",
      "38": "/images/48x48.png"
    }
  },
  "content_scripts": [
    {
      "css": [
        "styles.css"
      ],
      "js": [
        "content.js"
      ],
      "matches": [
        "https://mail.google.com/*"
      ]
    }
  ]
}