Stylesheet for GDPR Cookie Notice inexplicably disabled in Chrome inside Customizer preview

[westonruter]

As raised by @felixarntz to me, there is a strange issue whereby the GDPR cookie notice initially appears in the Customizer preview:

But then after ~5 seconds of loading the styles for the notice are just disabled. It's as if the stylesheet is removed from the DOM. Nevertheless, the style#wp-gdpr-cookie-notice-stylesheet element remains intact in the DOM. The unstyled notice looks like this (with position:fixed removed it then appears in the footer):

I added a DOM breakpoint to break on subtree modifications to the document and it breaks here immediately before the stylesheet gets disabled:

The link element being removed at this point (as reported by DevTools) is:

<link rel="preconnect" href="https://src.wordpress-develop.test" referrerpolicy="origin">

If I open dev tools and merely touch the contents of the style element (just click to edit but then click out without making any changes):

Then the stylesheet is somehow re-enabled and the notice gets re-styled.

I reproduced this issue in Chrome 67 and Chrome 69 (Canary). I could not reproduce the issue in Safari or Firefox.

(Note that the Customizer preview serves dirty AMP (that is, a non-valid AMP document) because the interface requires custom scripts and styles to live preview changes. This use of AMP is not officially supported.)

To reproduce the issue:

1. Install the latest develop build of the AMP plugin.
2. Activate the wp-gdpr-cookie-notice plugin
3. Activate one of the core themes, like Twenty Sixteen.
4. Go to the WP Admin > AMP and enable Native mode.
5. Access the Customizer in Chrome via /wp-admin/customize.php.
6. Wait 5 seconds after the edit shortcuts appear, and blink the notice disappears.

I suspect it could be a Blink bug.