Intent-to-Deprecate: amp-selector changing selection on low trust action

[sparhami]

Also, it doesn't seem correct that amp-selector should be able to toggle via a low trust action when it doesn't have a size defined layout (layout="container"). This means any low trust action (such as page scrolling via position observer) can cause the page layout to jump, which should not be the case.

Contrast this with carousel, which allows you to change slides on low trust action, but requires a defined size, so this cannot cause the page to jump.

As far as I know, amp-selector has the only low trust action in AMP that can affect page layout. My understanding of action trust is that this should not be the case.

Originally posted by @sparhami in #24425 (comment)

We want to deprecate low trust actions (e.g. scroll via amp-position-observer, slideChange via carousel's autoplay, video playback ending, etc) being able to affect page layout via <amp-selector>. The amp-selector component allows use of layout="container" and coupled with the fact that it sets an attribute, means that it can be used to affect page layout.

For example, this could be used with a 1px tall carousel and autoplay to cause an ad to jump into the middle of a page using the autoplay delay. It could also be used with amp-position-observer to cause an add to jump in when the user scrolls a certain distance.

We can still allow the selection to change if the amp selector itself has a defined layout size (i.e. not using layout="container").