Chrome 151 responsive iframe sizing

[chrisdavidmills]

Summary

Chrome 151 adds support for responsive iframe sizing; see https://chromestatus.com/feature/5108373464547328.

This relies on three new features:

• The CSS frame-sizing property
• The Window.requestResize method
• The <meta name=responsive-embedded-sizing> meta tag

This PR adds data for all three features.

Test results and supporting details

Related issues

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[Elchi3]

This is still behind the "Responsive Iframes" flag for me.
(Otherwise I would have caught it in collector runs already.)

[chrisdavidmills]

This is still behind the "Responsive Iframes" flag for me. (Otherwise I would have caught it in collector runs already.)

Ah, sorry about that. I'm sure the ChromeStatus page said 151 the other day.

I've had another look, and the ChromeStatus now says 152 for release. It doesn't work in Chrome beta, but it seems to work in Canary (the flag is enabled by default).

In which case, "preview" seems like the right value for now? Updated in my latest commit.

[Elchi3]

Thanks Chris! 👍

It wasn't in preview either but today it is.

I opened #29905 earlier this week and I'm not yet sure how often I want to run it. I think weekly might be good (or whenever I see new features). Still figuring this out.

[Elchi3]

Actually, I spoke too soon. I had the flag enabled and then it worked of course. I don't see this working in Canary yet without flags yet.

[chrisdavidmills]

Actually, I spoke too soon. I had the flag enabled and then it worked of course. I don't see this working in Canary yet without flags yet.

Hrm, this is different from what I experienced. I hadn't touched the "Responsive Iframes" flag on Canary (the value was kept at "default"), and it worked for me.

I had to explicitly set the flag to "disabled" to stop the feature working.

I've just tried updating Canary this morning to the latest, and the behavior is still the same for me.

I'm on macOS. They wouldn't have different flag settings on different OSes, would they?

[Elchi3]

I'm on macOS, too.

The test is here: https://collector.openwebdocs.org/tests/api/Window/requestResize. Reports no support without "Experimental web platform features". Works with that flag enabled.