manifest.json

{
  "manifest_version": 2,
  "name": "Productive",
  "version": "1.6.0",
  "description": "An extension to help keep track of tasks, notes, shortcuts and productivity.",
  "author": "Eric Liu",
  "icons": {
    "16": "assets/img/icon-16x16.png",
    "48": "assets/img/icon-48x48.png",
    "128": "assets/img/icon-128x128.png"
  },
  "browser_action": {
    "default_icon": "assets/img/icon-128x128.png"
  },
  "background": {
    "scripts": [
      "assets/js/tether.min.js",
      "assets/js/bootstrap.min.js",
      "assets/js/jquery-3.2.1.min.js",
      "assets/js/modernizr.min.js",
      "assets/js/string.js",
      "assets/js/script.js"
    ]
  },
  "chrome_url_overrides" : {
    "newtab": "index.html"
  },
  "permissions": [
    "background",
    "identity",
    "tabs",
    "https://www.googleapis.com/*",
    "https://*.googleusercontent.com/*",
    "https://mail.google.com/",
    "activeTab",
    "https://ajax.googleapis.com/"
  ],
  "short_name": "Productive",
  "content_security_policy": "script-src https://*.google.com 'unsafe-eval';   object-src 'self'",
  "oauth2": {
    "client_id": "<your client id>",
    "scopes": [
      "https://mail.google.com/"
    ]
  }
}