When viewing content on the Google CDN the AMP url menu overlays the amp-consent prompt iframe when in fullscreen mode.

To reproduce:

1. Visit https://www.google.com/amp/s/metro.co.uk/2019/06/25/cat-charity-boss-forced-pensioner-sleep-outside-eat-pet-food-10055967/amp/ on a device with EU Geo.
2. On the CMP prompt hit the Privacy Settings and policy link and note that the once fullscreen opens the AMP CDN url bar overlays the content.

I've tested on Samsung 9+ Chrome and Samsung Browser and on an iPhone XR Safari and the issue exists in all of them.

This issue does not happen when amp-lightbox is in fullscreen mode, the url bar correctly retracts / is hidden.

Relates to #22943

cc @zhouyx / @torch2424