Chrome extension: access to iFrame with a different domain

Question

I'm creating a basic Chrome extension that should apply some CSS styles to a specific website. In my manifest file I've added this domain. In some cases targeted website has an iframe with a different domain that I can't access it's content.

As I went throught the docs for Chrome developers, I've found two possible solutions:

1. Add "all_frames: true" option to the manifest.
2. Add domain of the iframe to the manifest.

None of this options helped me. I know that there are security limitations the restrict the cross-domain access. Is this the case or there is some way for the extension to access the iframes' content?

Currently my manifest file has this options:

"content_scripts": [
    {
      "all_frames": true,
      "matches": [
        "https://*.domain1.com/*",
        "https://prefix.domain2.com/*"
      ],
      "js": [
        "contentScript.js"
      ]
    }
  ]