Expansion panel headers inside a dialog jump size upon dialog open

[jelbourn]

Reproduction: https://stackblitz.com/edit/angular-pfrqah?file=src%2Fapp%2Fdialog-overview-example-dialog.html

The expansion panel headers start off with their expanded state height, and then quickly jump to their collapsed height. I suspect this has something to do with angular's animations, but it needs further investigation.

[jelbourn]

Yeah, disabling animations does eliminate the issue (setting [@.disabled]="true")
https://stackblitz.com/edit/angular-pfrqah-s61yu8?file=src%2Fapp%2Fdialog-overview-example-dialog.html

[crisbeto]

This is a long-standing issue and I'm pretty sure that we have other similar issue reports open. It happens, because of the behavior in @angular/animations where parent animations block all descendant animations.

I have a PR that tries to tackle it, but we never managed to land it and it might not be perfect, based on Andrew's comment. #11778

[crisbeto]

Closing this as a duplicate of #13870 which has been open for longer.

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