message: add minimum chrome version to manifest
diff: },
  "content_security_policy": "script-src 'self' 'unsafe-eval' https://www.google-analytics.com https://apis.google.com; object-src 'self'",
  "incognito": "split",
  - "offline_enabled": false
  + "offline_enabled": false,
  + "minimum_chrome_version": 51
  }
  