Intent to implement: partially drop restriction on `style` attributes

Some restrictions have to be preserved, but most can be dropped at this time, I believe.

Some considerations:

1. !important should be prohibited as with stylesheets (should be done already for SVG).
2. url() values (e.g. for background-image, etc) should be rewritable by cache (should be done already for SVG).
3. The only allowed values of position are static, relative (and absolute?).
4. Based on some future optimizations we want to do, we should probably also disallow top:X, left:X, right:X, bottom:X. Though we may be able to remove this restriction.
5. SSR should be able to work with publisher-authored style attributes.

The only real restrictions comparing to the current state of things are position and top/bottom/etc restrictions. The question is whether, given these restrictions, this is still a good idea to implement.

/cc @Gregable @honeybadgerdontcare @jpettitt

[aghassemi]

@jridgewell @nainar @dvoytenko I did a quick test and my conclusion is it does not block rendering for the whole document which is the big difference vs CSS in head. Chrome seems to progressively render and paint as document is streamed. In the following example, the first box is rendered immediately, the second box has a huge inline CSS that takes a bit to arrive, so that one and the next one are blocked.

https://storage.googleapis.com/ampconf-76504.appspot.com/test.html

Maybe we should put limit per element instead of an overall limit.

[Gregable]

The “for now” decision is simply just to move forward with implementation. It should probably not be construed as a decision on the limit we wish to have.